Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-01-13
2001-05-22
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S637000, C438S643000, C438S629000, C438S633000, C438S627000, C438S685000, C438S648000
Reexamination Certificate
active
06235632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the formation of a tungsten plug and more particularly, it relates to the formation of a barrier layer utilizing tungsten nitride prior to the chemical vapor deposition (CVD) of tungsten in a single chamber used for manufacturing a tungsten plug, for forming a contact gate in Flash EEPROM memory devices, and for forming local interconnects to CMOS gate structures.
2. Description of the Prior Art
As is generally well-known in the art of manufacturing of integrated circuits, a barrier layer is often required to be formed to prevent the diffusion of one type of material to another type of an adjacent material. In the past, titanium nitride (TN) had been used as the material for forming the diffusion barrier layer where conductive interfaces are needed to be maintained.
For example, in a conventional tungsten plug formation process, a sputtering or chemical vapor deposition (CVD) process is used for the formation of a titanium nitride layer on a substrate having a contact hole formed therein prior to the CVD of tungsten to fill the contact hole. However, since two different film formation processes are involved, there is required a first type of equipment for use in the deposition of the titanium nitride and a second different type of equipment for use in the deposition of the tungsten. As a result, the use of these two different process steps increases significantly the cost for the conventional tungsten plug formation process. In addition, in the formation of the conventional tungsten plug there is required a first subsequent process step to remove the tungsten and a second subsequent process step to remove the titanium nitride on the field region in order to form the tungsten plug, such as etching back and chemical-mechanical polishing (CMP). Therefore, since different chemistry is used in these removal steps, this also leads to a complicated process sequence.
It is apparent from the foregoing discussion that there still exists a need for a tungsten plug formation process, which requires only a single deposition chamber so as to reduce significantly the processing cost. This is achieved in the present invention by the formation of tungsten nitride by a plasma-enhanced CVD to be used as the barrier metal instead of titanium nitride, which is followed by a blanket tungsten film CVD made in the same deposition chamber.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a method for forming a barrier layer utilizing tungsten nitride prior to the chemical vapor deposition of tungsten in a single chamber.
It is an object of the present invention to provide a method of fabricating a tungsten plug utilizing a tungsten nitride layer prior to the chemical vapor deposition of tungsten in a single chamber so as to yield a higher through-put and a lower production cost.
It is another object of the present invention to provide a method for forming a contact gate in Flash EEPROM memory devices utilizing a tungsten nitride layer prior to the chemical vapor deposition of tungsten in a single chamber so that the tungsten nitride deposition is made without requiring a seed layer.
It is still another object of the present invention to provide a method for forming local interconnects to CMOS gate structures utilizing a tungsten nitride layer prior to the chemical vapor deposition of tungsten in a single chamber which exhibits a lower resistivity and a high thermal stability and is simpler to etch.
It is yet still another object of the present invention to provide a method for forming a barrier layer utilizing tungsten nitride prior to the chemical vapor deposition of tungsten in a single chamber so as to simplify the subsequent chemical-mechanical polishing process.
In accordance with a preferred embodiment of the present invention, there is provided a method of fabricating a tungsten plug at the via level. A metal line is formed in a top portion of a first insulating layer. A second insulating layer is formed on the first insulating layer and over an exposed surface of the metal line. The exposed surface of the metal line may be copper, copper silicide, or titanium nitride depending on the specific structure of the metal line. An etching process is applied to a region of the second insulating layer formed over the exposed surface of the metal line to create a contact hole within the region. The metal line is exposed in the region.
A tungsten nitride thin film is deposited over the second insulating layer and the exposed metal line. A blanket tungsten thin film is deposited successively to the depositing of the tungsten nitride thin film so as to fill the contact hole and to form a planar layer. A chemical-mechanical polishing is applied so as to remove the tungsten and tungsten nitride films on the field region in order to form tungsten-plugs.
In accordance with a second aspect of the present invention, the tungsten nitride thin film may be suitably used for forming contact gates in Flash EEPROM memory devices. In a third aspect of the present invention, the tungsten nitride thin film may be suitably used for forming local interconnects to CMOS gate structures.
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patent: 5939788 (1999-08-01), McTeer
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patent: 6093642 (2000-07-01), Cho et al.
patent: WO98/23389 (1998-06-01), None
Morales Guarionex
Ngo Minh Van
Nogami Takeshi
Advanced Micro Devices , Inc.
Bowers Charles
Chin Davis
Nguyen Thanh
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