Method of protecting tungsten plug from corroding

Details Method of protecting tungsten plug from corroding Method of protecting tungsten plug from corroding

1999-06-29

2001-08-21

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S622000, C438S648000, C438S656000, C438S669000, C438S704000, C438S745000, C438S749000, C438S906000

Reexamination Certificate

active

06277742

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 88107216, filed May 4, 1999, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method for fabricating a semiconductor device. More particularly, the present invention relates to a method of protecting a corrosion of tungsten plug.
2. Description of Related Art
In general, after forming a tungsten plug, a wire is formed to couple with the tungsten plug. While performing an etching process to pattern the wire, polymer is formed on sides of the wire. A wet cleaning process is then performed with a stripping solution to remove the polymer.
FIG. 1
is a schematic, cross-sectional diagram illustrating a situation where a wire is aligned over a tungsten plug.
Referring to
FIG. 1
, a tungsten plug
120
is formed in a substrate
100
, and a barrier layer
110
is formed between the substrate
100
and the tungsten plug
120
. A patterned wire
130
is formed on the substrate
100
. Normally, the wire
130
is aligned over the tungsten plug
120
and covers the entire tungsten plug
120
. The wire
130
protects the tungsten plug
120
from corroding while the wet cleaning process is performed with the stripping solution to remove the polymer on the sides of the tungsten plug
120
.
FIG. 2
is a schematic, cross-sectional diagram illustrating a situation where a wire is misaligned with a tungsten plug.
Referring to
FIG. 2
, a portion of the tungsten plug
120
is exposed when the wire
130
is misaligned over the tungsten plug
120
. While the wet cleaning process is performed with a stripping solution to remove the polymer on the sides of the tungsten plug
120
, the tungsten plug
120
is corroded by the stripping solution and a hole
140
is formed in the tungsten plug
120
.
The occurrence of tungsten corrosion is caused by charges accumulated on the wire. While performing the etching process to form the wire
130
, the charges are accumulated on the wire
130
; thus, a great electrical potential is generated between the tungsten plug
120
and the wire
130
. As a result, the exposed tungsten is oxidized to an ionic state such as WO
4
−2
by the stripping solution whose pH value is about 10 to about 12 and dissolved into the stripping solution during the wet cleaning process. Therefore, the hole
140
is formed.
In Bothra et al. (IEEE 98 CH36173.36 Annual International Reliability Physics Symposium, 1998. pp. 150-156), a method to avoid the occurrence of tungsten corrosion is provided. The substrate is dipped into a neutral ionic solution such as deionized water for several hours, and then the wet cleaning process is performed. By dipping the substrate into the neutral ionic solution, the charges accumulated on the wire are discharged; thus, the tungsten plug can be protected from corrosion during the wet cleaning process. However, although the tungsten plug is protected, the wire is corroded by being dipped into the neutral ionic solution. Another method is that the charges are discharged by an electron beam. However, an electron beam machine is not generally used in the manufacturing processes.
SUMMARY OF THE INVENTION
The invention provides a method of protecting a tungsten plug from corroding. By the method, an occurrence of tungsten corrosion is avoided during a wet cleaning process.
As embodied and broadly described herein, the invention provides a method of protecting a tungsten plug from corrosion. After a tungsten plug is formed in a substrate, a wire is then formed on the tungsten plug over the substrate. The substrate is dipped into an electrolyte solution. Then, a wet cleaning process is performed to remove polymer formed on the wire.
In the invention, the substrate is only dipped into the electrolyte solution for a short time interval. Then, the charges accumulated on the wire are discharged. As a result, the occurrence of tungsten corrosion is avoided while the subsequent wet cleaning process is performed.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 6077762 (2000-06-01), Liang et al.
patent: 6153531 (2000-10-01), Bothra et al.
patent: 50-036935 (1975-04-01), None

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