Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2003-07-14
2004-08-10
Gurley, Lynne (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S648000, C438S656000, C438S658000, C438S660000, C438S685000, C438S768000, C438S785000
Reexamination Certificate
active
06774029
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a conductive film and a conductive pattern of a semiconductor device. More particularly, the present invention relates to a method for forming a conductive film and a conductive pattern of a semiconductor device without a failure between conductive films or conductive patterns.
2. Description of the Related Art
Highly integrated semiconductor devices are required to stay in step with a rapidly developing information society. As a result, dimensions of electrical wirings of a semiconductor device are becoming more minute, and intervals between the electrical wirings are increasingly reduced. As the dimensions of the electrical wirings decrease, resistances in the conductive patterns or lines that function as the electrical wirings remarkably increase. Thus, the electrical wirings of the semiconductor device should be formed using materials having much lower resistances than those previously used.
In general, a conductive pattern primarily forms the semiconductor device. For example, a gate electrode or a bit line is formed using polysilicon or metal silicide having a relatively high resistance. Recently, the conductive pattern is formed using tungsten (W) because tungsten has a resistance lower than that of polysilicon or metal silicide and manufacturing processes for the semiconductor device are stably performed when tungsten is used.
FIGS. 1A and 1B
illustrate cross-sectional views of a conventional method for forming a tungsten pattern of a semiconductor device.
Referring to
FIG. 1A
, a tungsten film is formed on a semiconductor substrate
10
. Then, after a photoresist pattern
14
is formed on the tungsten film, the tungsten film is etched using the photoresist pattern
14
as an etching mask to from a tungsten pattern
12
on the semiconductor substrate
10
.
Referring to
FIG. 1B
, the photoresist pattern
14
on the tungsten pattern
12
is removed. The photoresist pattern
14
may be removed through an ashing process and a stripping process. However, a side portion of the tungsten pattern
12
is partially or entirely oxidized during the ashing process because tungsten reacts rapidly with oxygen, thereby forming a tungsten oxide film
16
at the side portion of the tungsten pattern
12
.
When a successive thermal process is performed concerning the tungsten pattern
12
having the tungsten oxide film
16
formed thereon, the tungsten oxide film
16
may abnormally grow from the side portion of the tungsten pattern
12
according to a reaction between the tungsten oxide film
16
and oxygen in the ambient atmosphere.
FIG. 2
illustrates a cross-sectional view showing a failure between tungsten patterns due to abnormally grown tungsten oxides.
As shown in
FIG. 2
, the abnormally grown tungsten oxide film
18
(called a “whisker”) electrically connects one tungsten pattern
12
with an adjacent tungsten film, thereby generating a fatal failure between the tungsten patterns.
To overcome such a failure between the tungsten patterns, the prior art discloses a method of removing the tungsten oxide with a solution containing sulfuric acid or a mixture of sulfuric acid and hydrogen peroxide. However, the tungsten oxide may not be completely removed by those methods using the above-mentioned etching solutions.
SUMMARY OF THE INVENTION
In an effort to solve the problems mentioned above, it is a first feature of an embodiment of the present invention to provide a method of forming a conductive film without a failure between conductive films during a series of successive thermal processes.
It is a second feature of an embodiment of the present invention to provide a method of forming a conductive pattern without a failure between conductive patterns during a series of successive thermal processes.
In order to provide the first feature of an embodiment of the present invention, there is provided a method for forming a conductive film of a semiconductor device including i) nitrifying a semiconductor substrate on which a tungsten film having a partially oxidized surface is formed, to form a tungsten nitride film on the surface of the tungsten film, ii) oxidizing the surface of the tungsten film having the tungsten nitride film to change the tungsten nitride film into a tungsten oxy-nitride film; and iii) removing the tungsten oxy-nitride film and any residue generated by a reaction of tungsten from the surface of the tungsten film, to form a tungsten film.
In the method above, i) is preferably performed through a rapid thermal nitrification method or a plasma process using a gas including a nitrogen compound. If the plasma process is used, the plasma process is preferably performed at an energy of approximately 200 to 1000 W using at least one reaction gas selected from the group consisting of NH
3
gas, NF
4
gas and N
2
gas.
In the method above ii) is preferably performed through a rapid thermal oxidation process or a plasma process using an oxygen gas. In iii) of the method above, the tungsten oxy-nitride film is preferably removed using an etching solution for etching oxide. Preferably, the etching solution includes hydrofluoric acid or a mixture of hydrofluoric acid and hydrogen peroxide.
To provide the second feature of an embodiment of the present invention, there is provided a method for forming a conductive pattern of a semiconductor device including i) forming a conductive film mainly composed of tungsten on a semiconductor substrate; ii) forming a photoresist pattern on the conductive film; iii) forming a conductive pattern by etching the conductive film using the photoresist pattern as an etching mask; iv) removing the photoresist pattern while a surface of the conductive pattern is partially oxidized; v) nitrifying the conductive pattern including the partially oxidized surface to change the tungsten in the surface of the conductive pattern into a tungsten nitride film; vi) oxidizing the conductive pattern including the tungsten nitride film formed thereon to change the tungsten nitride film formed on the surface of the conductive pattern into a tungsten oxy-nitride film; and vii) forming a conductive pattern without an oxide on the conductive pattern by removing the tungsten oxy-nitride film.
In the method above, vi) is preferably performed by a rapid thermal oxidation process or a plasma process using an oxygen gas.
To provide the second feature according to another embodiment of the present invention, there is provided a method for forming a conductive pattern of a semiconductor device including i) forming a conductive film mainly composed of tungsten on a semiconductor substrate; ii) forming a photoresist pattern on the conductive film; iii) forming a conductive pattern on which the photoresist pattern is formed by etching the conductive film using the photoresist pattern as an etching mask; iv) nitrifying the conductive pattern to change the tungsten in a side portion of the conductive pattern into a tungsten nitride film; v) removing the photoresist pattern using a gas including oxygen, and simultaneously changing the tungsten nitride film into a tungsten oxy-nitride film; and vi) forming a conductive pattern without an oxide on the conductive pattern by removing the tungsten oxy-nitride film.
In the method above, v) is preferably performed by a plasma process using an oxygen gas.
In the two most recent methods above, the conductive film preferably includes a tungsten film and a tungsten suicide film; nitrifying the conductive pattern is preferably performed by a rapid thermal nitrification process or a plasma process using a gas including a nitrogen compound. If the plasma process is used to nitrify the conductive pattern in the methods above, the plasma process is preferably performed at an energy of approximately 200 to 1000 W using at least one reaction gas selected from the group consisting of NH
3
gas, NF
4
gas and plasma N
2
gas. Also, in the two most recent methods above, the tungsten oxy-nitride film is preferably removed using an etching solu
Lee Hyeon-Deok
Park Hong-mi
Park In-Sun
Shin Ju-Cheol
Gurley Lynne
Lee & Sterba, P.C.
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