Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-07-20
2003-06-17
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S601000, C438S680000, C438S686000, C438S688000
Reexamination Certificate
active
06579794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tungsten layer formation method for a semiconductor device, and more particularly, to a tungsten layer formation method for a semiconductor device that reduces the resistivity of the tungsten layer and a semiconductor device using the same.
2. Description of the Related Art
Generally, a semiconductor device is manufactured by sequentially forming multiple layers, such as a polycrystalline layer, an oxide layer, an insulating layer and a metal layer, etc. on a semiconductor substrate (e.g., a wafer), and forming patterns thereon according to the characteristics of the semiconductor device through conventional photolithography, etching and ion-implantation processes.
As the design rule for highly-integrated semiconductor devices continues to decrease, the aspect ratio of contact holes within such devices continues to increase. As a result of the increased aspect ratio, an aluminum layer can not be easily buried inside the contact holes using conventional sputtering methods. Recently, a CVD (Chemical Vapor Deposition) method has been introduced for depositing metal by way of a chemical reaction after vaporizing certain metal chemicals. A widely used method is a tungsten (W) CVD method which exhibits good contact hole burial characteristics.
The conventional CVD tungsten layer formation method is described with reference to FIG.
1
. First, an insulating layer
11
such as an oxide layer or the like is formed on the semiconductor substrate
10
. Thereafter, a portion of the insulating layer
11
is removed, by patterning and etching for example, so as to form contact holes
12
.
A barrier metal layer
16
is then formed on the insulating layer
11
, with the barrier metal layer
16
comprising a titanium (Ti) layer
13
and a titanium nitride (TiN) layer
15
, each having a thickness of about 700 Å, which are sequentially formed. The surface of the barrier metal layer
16
is treated using SiH
4
gas under a pressure environment of between 4.5 to 40 Torr.
Then, a tungsten seed layer (not shown) is formed on the barrier metal layer
16
using WF
6
and SiH
4
gas with the mixing ratio of the gases {WF
6
}: {SiH
4
} being about 1:1 to 3:1, under the same pressure environment as above, that is, 4.5 to 40 Torr. Thereafter, a tungsten layer
18
of about 4400 Å in thickness is formed on the treated barrier metal layer
16
using WF
6
and H
2
.
Although the tungsten layer
18
formed as described above is easily buried inside the contact hole, the resistivity (&rgr;: &mgr;&OHgr;·cm) is four to five times as high as the aluminum layer used for conventional metal pattern lines. As a result, the operational speed of the semiconductor device is decreased and the power consumption is increased when using the tungsten metal pattern lines.
When the tungsten layer
18
having a polycrystalline structure is formed as described above, the average grain size of the tungsten layer
18
is about 2000 to 2500 Å and the area encompassed within the grain boundary is increased,thereby increasing the resistivity because of the increase in electrical resistance within the boundary.
In an attempt to overcome this problem, some have added diborane (B
2
H
6
) gas to reduce the resistivity of the tungsten layer during the formation of the tungsten layer. By adding diborane (B
2
H
6
) gas during the tungsten layer formation, the grain size of the tungsten layer having a polycrystalline structure is increased to thereby reduce the resistance. As a result, the resistivity of the tungsten layer may be reduced from about 11.4-11.7 &mgr;&OHgr;·cm down to about 8-9 &mgr;&OHgr;·cm.
However, there are drawbacks to using this technique, for example, the requirement for installing a separate diborane gas line and mass flow controller. In addition, there is a decrease in the burial characteristics of the tungsten layer and the process window.
Others in the art have formed metal pattern line structures wherein a tungsten plug is formed inside the contact hole, and an aluminum layer is formed thereon. In this manner, the defects experienced with the burial characteristics of the aluminum layer, and the problems with the high resistivity of the tungsten layer have been minimized.
Again there are drawbacks to using this technique because during the formation of the metal pattern lines comprising a tungsten plug and an aluminum layer, a planarization process such as CMP (Chemical Mechanical Polishing) or Etch Back should be additionally carried out after forming the tungsten layer for the tungsten plug. The planarization process increases both the processing time and costs for manufacturing semiconductor devices. Further, there is a possibility of additional process failures occurring during the planarization process.
SUMMARY OF THE INVENTION
The present invention is directed to providing a tungsten layer formation method for a semiconductor device that reduces the resistivity of the tungsten layer without the need to alter the conventional manufacturing system.
To achieve this and other advantages and in accordance with the purposes of the present invention, the tungsten layer formation method for semiconductor devices includes treating the surface of a barrier metal layer formed over a semiconductor substrate in a pressure environment of over 40 Torr using SiH
4
gas. A tungsten seed layer is then formed on the treated barrier metal layer using WF
6
and SiH
4
gases, with the mixing ratio {WF
6
}/{SiH
4
} of the gases being less than or equal to 1. A tungsten layer is thereafter formed on the treated barrier metal layer having the tungsten seed layer formed thereon. The tungsten layer is formed by supplying WF
6
gas or a mixed gas of WF
6
and H
2
gas. The barrier metal layer comprises a titanium (Ti) layer and a titanium nitride (TiN) layer, which are sequentially formed.
Preferably, the treating is carried out in a pressure environment of over 90 Torr. Also, the tungsten seed layer is formed in a pressure environment that is less than atmospheric pressure, and preferably, the tungsten seed layer is formed in a pressure environment of between 4 and 5 Torr.
In another aspect of the present invention, a tungsten layer formation method for semiconductor devices includes forming an insulating layer over a semiconductor substrate; forming contact holes in the insulating layer; forming a barrier metal layer along the inner wall of the contact holes; treating the surface of the barrier metal layer using SiH
4
gas in a pressure environment of over 40 Torr; forming a tungsten seed layer on the surface of the treated barrier metal layer using WF
6
and SiH
4
gases in which the ratio {WF
6
}/{SiH
4
} of the gases is less than or equal to 1; and forming a tungsten layer over the treated barrier metal layer having the tungsten seed layer using WF
6
gas mixed with H
2
gas. The barrier metal layer comprises a titanium (Ti) layer and a titanium nitride (TiN) layer, which are sequentially formed.
Preferably, the treating is carried out in a pressure environment of over 90 Torr. Also, the tungsten seed layer is formed in a pressure environment that is less than atmospheric pressure, and preferably, the tungsten seed layer is formed in a pressure environment of between 4 and 5 Torr.
In another aspect of the present invention, a semiconductor device includes an insulating layer over a semiconductor substrate, a contact hole formed inside the insulating layer, a barrier metal layer formed along the inner wall of the contact hole, and a tungsten layer formed on the barrier metal layer, the tungsten layer being formed by treating the surface of the barrier metal layer using SiH
4
in a pressure environment of over 40 Torr, forming a tungsten seed layer on the treated surface of the barrier metal layer using WF
6
and SiH
4
gases, in which the ratio {WF
6
}/{SiH
4
} of the gases is less than or equal to 1, and forming a tungsten layer over the treated b
Baek Hong-Joo
Kim Hun-ki
Kim Kyung-tae
Oh Seong-tae
Berry Renee R
Nelms David
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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