Low resistivity poly-silicon gate produced by selective...

Details Low resistivity poly-silicon gate produced by selective... Low resistivity poly-silicon gate produced by selective...

1999-09-23

2001-02-06

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S197000, C438S585000, C438S643000, C438S647000, C438S648000, C438S649000, C438S655000

Reexamination Certificate

active

06184129

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to the field of integrated circuits, and more particularly, to the fabrication of semiconductor integrated circuit gates having a low resistivity polymetal silicide.
BACKGROUND OF THE INVENTION
Without limiting the scope of the invention, its background is described in connection with the formation of polysilicon containing conductor gates, as an example.
As is well known in the art of integrated circuit design, layout and fabrication, the manufacturing cost of a given integrated circuit is largely dependent upon the chip area required to implement desired functions. The chip area is defined by the geometries and sizes of the active components disposed in the wafer substrate. Active components include gate electrodes in metal-oxide semiconductors (MOS) and diffused regions such as MOS source and drain regions and bipolar emitters, collectors and base regions.
SUMMARY OF THE INVENTION
What is needed is a structure and method for using current integrated circuit processing techniques and manufacturing equipment that meet the demands of VLSI and ULSI integrated circuits. One particular area of need is for a low resistivity polymetal silicide conductor/gate. The polymetal silicide conductor/gate should be reliable and formed using existing equipment. Metal as used and defined herein is meant to include metal silicides.
Also needed is a polymetal silicide conductor/gate that is obtained using a simplified process flow and in which the oxidation of the metal layer is reduced. Finally, a need has arisen for a simplified process for forming a polymetal silicide conductor/gate that is economical to make using existing techniques and materials.
One embodiment of the present invention is directed to a method of fabricating a polymetal silicide conductor/gate comprising, forming polysilicon and sacrificial material into a conductor and a gate over a gate oxide. A sacrificial material may be made with, e.g., silicon nitride or phosphosilicate glass (PSG). Gate sidewalls can also be created to protect the sides of the polysilicon and the sacrificial material. The sacrificial material is stripped to expose the top surface of the polysilicon and a diffusion barrier is deposited over the exposed polysilicon. Following deposition of the diffusion barrier, a metal layer is selectively grown on the diffusion barrier to form a gate contact. Finally, a dielectric layer is deposited over the selectively formed metal and the gate oxide.
In one embodiment of the present invention the diffusion barrier that is deposited over the exposed polysilicon is made by depositing tungsten nitride on the exposed polysilicon and annealing the tungsten nitride to form a tungsten silicon nitride. In another embodiment of the invention, the step of forming a diffusion barrier over the exposed polysilicon comprises the steps of, depositing titanium on the exposed polysilicon to form a titanium silicide, removing the excess unreacted titanium with a titanium selective etch and exposing the titanium silicide to a nitrogen plasma to form a titanium silicon nitride. Yet another method of depositing a diffusion barrier over the exposed polysilicon comprises the steps of forming a titanium silicide layer on the exposed polysilicon by reacting the exposed surface with titanium tetrachloride in the presence of silane.


REFERENCES:
patent: 5027185 (1991-06-01), Liauh
patent: 5336903 (1994-08-01), Ozturk et al.
patent: 5381302 (1995-01-01), Sandhu et al.
patent: 5912487 (1999-06-01), Hong

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