Semiconductor device manufacturing: process – Chemical etching – Combined with coating step
Reexamination Certificate
2002-04-11
2004-02-17
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Chemical etching
Combined with coating step
C438S708000, C438S709000, C216S054000, C216S063000, C216S066000, C216S079000
Reexamination Certificate
active
06693040
ABSTRACT:
This application claims the benefit of the Korean Application No. P2001-62127 filed on Nov. 13, 2001, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a metal line of a semiconductor device, and more particularly, to a method for cleaning a contact area of a metal line in which a nitride barrier layer is formed at a sidewall of an insulating interlayer within the contact area by injecting a nitrogen-based radical into the contact area, so that it is possible to prevent a low dielectric insulating interlayer from becoming deteriorated by the redeposition of metal ions and by hydrogen radicals activated during reactive cleaning, thereby maintaining a low dielectric characteristic of the insulating interlayer.
2. Discussion of the Related Art
In general, dama cleaning has been attractive as a technology that can be applicable to a multilayered metal line technology. Dama cleaning means that a metal oxide layer formed at an exposed upper part of a metal line is removed before depositing a contact metal.
The basic mechanism of dama cleaning is an etch process utilizing a dual frequency etch (DFE). That is, the dama cleaning includes a physical method caused by the collision of activated Ar
+
molecules with the metal oxide layer, and a chemical method using oxidation and reduction reactions of the hydrogen H
2
radical and elements of the metal oxide layer within a pattern, thereby removing the metal oxide layer.
A process for removing the metal oxide layer is called as the dama cleaning in that Cu substitutes for Aluminum as a line material to obtain ultrahigh speed of a device, so that damascene structure is usually used in forming the contact area of the metal line since the related art dry etch cannot be applicable to Cu line. In the damascene structure, it is required to remove the residue of the contact area like the related art process, therefore, the process for removing the metal oxide layer is called as the dama cleaning.
A cleaning method of the contact area of a metal line according to the related art dama cleaning method will now be described with reference to the accompanying drawings.
In below embodiments, a metal line is formed of Cu.
FIG. 1A
to
FIG. 1E
are cross sectional views illustrating manufacturing process steps of the method for cleaning the contact area of the related art metal line.
As shown in
FIG. 1A
, a metal line
12
is formed on a substrate
11
. Next, a first nitride layer
13
, an insulating interlayer
14
, a cap oxide layer
15
and a second nitride layer
16
are sequentially deposited and then are selectively removed to expose the metal line
12
, thereby forming a contact area.
At this time, the insulating interlayer
14
is formed of a low dielectric (low-k) insulating material, so that the parasitic capacitance of the device is decreased, thereby obtaining a high operating speed.
As time goes by, the exposed metal line
12
is in contact with the air, thereby generating an oxide layer. Since the metal oxide layer and residue
17
, such as a photoresist generated after photolithography, cause a deterioration of the contact characteristics between metals, the metal oxide layer and the residue, such as the photoresist are removed during cleaning. Especially in the case when the contact structure is of the damascene type, dama cleaning is used.
As described above, the dama cleaning method includes a sputtering process using Ar
+
and a reactive cleaning process using a hydrogen H* radical.
As shown in
FIG. 1B
, the exposed residue
17
(metal oxide layer and the residue such as the photoresist) is etched by sputtering Ar.
The Ar
+
sputtering etch is a physical method in which Ar
+
molecules are sputtered against the surfaces of the residue
17
to remove the residue, thereby exposing the metal line
12
.
Referring to
FIG. 1C
, even though it is possible to remove the residue
17
, e.g., the metal oxide layer by the Ar
+
sputtering etch, an over etch is generated to remove the metal oxide layer, whereby a metal of the etched region is redeposited at a sidewalls of the insulating interlayer.
That is, the contact area lateral diffusion of the metal is generated, thereby causing a deterioration in the characteristics of the insulating interlayer in maintaining the low dielectric characteristic.
As shown in
FIG. 1D
, after applying the Ar
+
sputtering etch, a reactive cleaning is performed by directing a hydrogen H* radical to the remaining portion of the metal oxide layer.
For example, if the hydrogen radical H* and the metal line of the metal oxide layer are formed of Cu, a chemical reaction of the following formulae is expected [Cu
2
O+2H*->2Cu+H
2
O] or [Cu
2
O+H*->2Cu+OH*].
Accordingly, the metal oxide layer is reduced to the metal by reactive cleaning. Also, OH* and H
2
O of a radical state are generated and absorbed into the insulating interlayer.
That is, the reactive byproducts, such as OH* and H
2
O are generated during the reactive cleaning, thereby causing a deterioration in the low dielectric characteristics of the insulating interlayer.
As shown in
FIG. 1E
, the metal oxide layer is mostly removed after the reactive cleaning using the hydrogen H* radical. At this time, Cu ions redeposited at the sidewall of the insulating interlayer and the reactive byproducts such as H
2
O and OH* radical are not perfectly removed.
The residue at the sidewall of the insulating interlayer is absorbed into the insulating interlayer, thereby deteriorating the low dielectric characteristic of the insulating interlayer.
The related art cleaning method of the contact area of the metal line has the following problems.
In general, the dama cleaning includes the physical method sputtering Ar
+
molecules activated to the metal oxide layer, and the chemical method reducing the metal oxide layer to the metal by the hydrogen H* radical.
However, in case using Ar
+
molecules, the over etch may be generated, so that the metal is redeposited at the sidewall of the insulating interlayer within the contact area. In case using hydrogen radical, the reactive byproducts remain at the sidewall, and then are soaked and absorbed.
Also, the byproducts remaining at the sidewall of the insulating interlayer generates deterioration of adhesion between the contact metal of the contact area and the insulating interlayer.
As a result, the low dielectric characteristic of the insulating interlayer is lost, so that it is impossible to maintain insulating characteristic except the contact area, thereby deteriorating characteristic of the semiconductor device.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method for cleaning a contact area of a metal line that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a method for cleaning a contact area of a metal line in which a nitride barrier layer is formed at a sidewall of an insulating interlayer within the contact area by injecting nitrogen-based radical into the contact area, so that it is possible to prevent a low dielectric insulating interlayer from being deteriorated by redeposition of metal ions and by hydrogen radical activated during reactive cleaning, thereby maintaining a low dielectric characteristic of the insulating interlayer.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and bro
Berry Renee R.
Birch & Stewart Kolasch & Birch, LLP
Hynix / Semiconductor Inc.
Nelms David
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