Method of forming gate electrode in semiconductor device

Details Method of forming gate electrode in semiconductor device Method of forming gate electrode in semiconductor device

1999-12-17

2001-02-27

Smith, Matthew (Department: 2825)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

Insulated gate formation

C438S622000, C438S592000, C438S593000, C438S657000

Reexamination Certificate

active

06194294

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a gate electrode having a stacked structure of a polysilicon layer and a refractory metal layer in a semiconductor device.
2. Description of the Related Art
Since a gate resistivity is important factor in the manufacture of highly integration of semiconductor device, the gate electrode is formed to a stacked structure of a polysilicon layer and a refractory metal, for reducing the gate resistivity. A tungsten(W) layer is used as the refractory metal. A barrier metal layer is also interposed between the polysilicon layer and the tungsten layer to prevent diffusion therebetween. The barrier metal layer is formed of a titanium nitride(TiN) layer or a tungsten nitride(WN) layer. Furthermore, for removing damage and residues due to the etching process and recovering the reliability of a gate oxide layer after forming the above gate electrode, gate re-oxidation process is performed.
In the gate re-oxidation process, however, the volume of the tungsten layer expands due to its fast oxidation rate, so that the morphology of the gate electrode is transformed. Therefore, it is difficult to perform ion-implantation for forming a source and a drain. Furthermore, gate resistivity increases.
To overcome the above problems, as the gate re-oxidation process, a selective oxidation process which oxidize selectively the only polysilicon layer, is suggested. However, since the selective oxidation process is performed at the high temperature, there is another problem that thermal budget occurs.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of forming a gate electrode in a semiconductor device which can easily perform gate re-oxidation process without transforming the morphology of the gate electrode, for solving the problems in the conventional art.
To accomplish this above object, according to the present invention, a gate oxide layer, a doped polysilicon layer, a barrier metal layer and a refractory metal layer are formed on a semiconductor substrate, in sequence. A hard mask is then formed on the refractory metal. Next, the refractory metal layer, the barrier metal layer and the polysilicon layer are etched using the hard mask as an etch mask to form a gate electrode. A spacer for oxidation barrier is then formed on the side walls of the gate electrode and the hard mask. Thereafter, gate re-oxidation process is performed using the spacer as an oxidation mask to form a re-oxidation layer on the substrate of both sides of the spacer.
In this embodiment, the spacer is formed of a nitride layer such as a SiON layer or a Si
4
N
3
layer. Furthermore, the spacer is formed to the thickness of 50 to 300 Å.
Additional object, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.


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