Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-01-23
2001-09-18
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S584000, C438S618000, C438S643000, C438S680000
Reexamination Certificate
active
06291342
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of forming a titanium nitride film and a method of manufacturing a semiconductor device using the same.
2. Description of the Related Art
An adhesive layer having a Ti/TiN structure is generally employed in order to improve the poor adhesive characteristic of a metal such as tungsten (W) for filling a contact hole, when a metal contact plug required for the metal wiring of a semiconductor device is formed.
In a conventional technology, a physical vapor deposition (PVD) method such as a sputtering method is used for forming the adhesive layer having the Ti/TiN structure. However, when the Ti/TiN structure is formed by the PVD method, a film having a poor step coverage is obtained. Therefore, in the case of forming a contact having a large aspect ratio, the overhang of the Ti/TiN film is severe at the entrance of the contact hole when the Ti/TiN film is used as the adhesive layer or a barrier layer. Accordingly, a large void is formed in the contact during a subsequent process of depositing a tungsten film. Also, when the Ti/TiN film is too thin on the bottom of the contact due to the poor step coverage of the Ti/TiN film, WF
6
, gas, used as a source gas during a subsequent process of depositing the tungsten film, and Ti of the Ti/TiN film react, thus forming a nonconductor or vaporizing some part. Accordingly, the TiN film is lifted and peeled off. If so, the Ti/TiN film cannot serve as a barrier with respect to the WF
6
gas.
Therefore, a process of forming a TiN film by a chemical vapor deposition
In particular, the TiN film formed by the CVD method using TiCl
4
gas as a source gas is generally used as an adhesive layer of a metal film or a barrier film when a metal contact or a capacitor is formed since it is possible to obtain a good step coverage.
A large amount of chlorine (Cl) is included in the formed TiN film in the method of forming the TiN film by the CVD method using the TiCl
4
gas as the source gas. The TiN film containing a large amount of Cl shows a high resistivity. Also, since Cl permeates and damages the Ti film which is an underlayer, a high temperature rapid thermal nitration (RTN) process, or an NH
3
plasma process is required on the Ti film in order to prevent the Cl permeation.
When the high temperature RTN process or the NH
3
plasma process is performed with respect to the Ti film, the following problems occur. Firstly, the number of processes increases and a semiconductor manufacturing process becomes complicated since the above process is added. Secondly, additional equipment should be introduced since the above process is added. As a result, the burden of equipment investment increases. Thirdly, shallow junctions have recently started to be realized in semiconductor devices. Therefore, the allowed thickness of the Ti film deposited as the barrier film in the contact hole is restricted. However, a considerable amount of Ti is consumed in the Ti film by the high temperature RTN process or the NH
3
plasma process. As a result, it is not possible to secure a stable contact resistance since the amount of residing Ti becomes small.
SUMMARY OF THE INVENTION
To solve the above problem(s), it is an objective of the present invention to provide a method of forming a multilayer TiN film so as to lower the amount of Cl in a TiN film introduced when the TiN film is formed by a chemical vapor deposition (CVD) method such that the device does not deteriorate.
It is another objective of the present invention to provide a method of manufacturing a multilayer TiN film by which it is possible to simplify a process by reducing the number of process steps.
It is still another objective of the present invention to provide a method for manufacturing a semiconductor device using the TiN film formed by the above method.
Accordingly, to achieve the first and second objectives, there is provided a method of forming a multilayer TiN film by a chemical vapor deposition (CVD) method on a semiconductor substrate on which an underlayer is formed. In this method, an underlayer protective TiN film is formed on the underlayer. A main TiN film is formed on the underlayer protective TiN film.
The underlayer is a Ti film. At this time, NH
3
gas may be pre-flown on the surface of the Ti film before the step (a).
The step (a) comprises the steps of (a-
1
) forming a first TiN film on the underlayer to have a thickness of between 10 and 100 Å using a source gas composed of a mixture of TiCl
4
gas and NH
3
gas and (a-
2
) annealing the first TiN film in an NH
3
gas atmosphere.
The step (b) comprises the steps of (b-
1
) forming a second TiN film on the underlayer protective TiN film using a source gas formed of a mixture of TiCl
4
gas and NH
3
gas and (b-
2
) annealing the second TiN film in the NH
3
gas atmosphere.
The gas flow ratio of TiCl
4
to NH
3
is between 0.02 and 0.1 in the source gas.
The first and second TiN films are formed under a pressure of between 0.2 and 0.5 Torr and at a temperature of between 530 and 680° C.
The steps of annealing the first TiN film and the second TiN film are respectively performed at a temperature of between 530 and 680° C.
The step (c) of forming an oxygen diffusion preventing TiN film on the main TiN film can be further comprised after the step (b).
The step (c) comprises the steps of (c-
1
) forming a third TiN film on the main TiN film using a source gas composed of a mixture of TiCl
4
gas and NH
3
gas, to have a thickness of between 10 and 100 Å and (c-
2
) annealing the third TiN film in the NH
3
gas atmosphere.
The third TiN film is formed under a pressure of between 0.2 and 0.5 Torr and at a temperature of between 530 and 680° C.
In order to form the main TiN film, a TiN film is formed on the underlayer protective TiN film to have a thickness of between 10 and 100 Å using a source gas formed of a mixture of TiCl
4
gas and NH
3
gas. The TiN film is annealed in an NH
3
gas atmosphere. The above steps are repeated until the main TiN film having a desired thickness is obtained.
Also, to achieve the above objectives, a first TiN film covering the underlayer exposed on a semiconductor substrate is formed by a chemical vapor deposition (CVD) method using a source gas supplied in a first gas flow ratio having a predetermined TiCl
4
to NH
3
gas flow ratio. The first TiN film is annealed in an NH
3
gas atmosphere to form an underlayer protective TiN film. A second TiN film is formed on the underlayer protective TiN film by the CVD method, using a source gas supplied in a second gas flow ratio having a TiCl
4
to NH
3
gas flow ratio larger than the first gas flow ratio. The second TiN film is annealed in an NH
3
gas atmosphere to form a main TiN film.
The first gas flow ratio and the second gas flow ratio are selected to be between 0.02 and 0.1, respectively. The first gas flow ratio is selected to be between 0.02 and. 0.05.
The step of forming the first TiN film and the step of forming the second TiN film are respectively performed under a pressure of between 0.2 and 0.5 Torr and at a temperature of between 530 and 680° C.
The steps of annealing the first TiN film and the second TiN film are respectively performed at a temperature of between 530 and 680° C.
After forming the main TiN film, a third TiN film is formed on the main TiN film using a source gas supplied in a third gas flow ratio having a TiCl
4
to NH
3
gas flow ratio which is smaller than the second gas flow ratio. The third TiN film is annealed in an NH
3
gas atmosphere.
The third gas flow ratio is selected to be between 0.02 and 0.1.
Also, to achieve the above objectives, in the present invention, a first TiN film covering the underlayer exposed on a semiconductor substrate by the CVD method, using a source gas supplied in a first gas flow ratio having a predetermined TiCl
4
to NH
3
gas flow ratio. A second TiN film is formed on the first TiN film by the CVD method, using a so
Chung Ju-hyuck
Lee Jang-eun
Seo Tae-wook
Anya Igwe U.
Myers Bigel & Sibley & Sajovec
Samsung Electronics Co,. Ltd.
Smith Matthew
LandOfFree
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