Coating processes – Coating by vapor – gas – or smoke – Mixture of vapors or gases utilized
Reexamination Certificate
2002-12-02
2004-11-30
Meeks, Timothy (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Mixture of vapors or gases utilized
C427S255391, C427S255394
Reexamination Certificate
active
06824825
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method for depositing a metallic nitride series thin film, typically a TiN-series thin film, which is used as, e.g., a barrier layer, a capacitor top electrode, a gate electrode or a contact part, in a semiconductor device.
2. Description of the Related Art
In the production of semiconductor devices, the construction of circuits tends to have a multilayer metallization structure on a recent demand for higher density and higher density integration. Therefore, an embedding technique for electrical connections between layers, such as a contact hole which is a connecting part between a bottom semiconductor device layer and a top wiring layer, and a via hole which is a connecting part between top and bottom wiring layers, is important. In addition, with the high-density integration, a technique for depositing a top electrode of capacitor gate material of a DRAM memory part, at a high coverage is important. Recently, a high dielectric material, such as Ta
2
O
5
, is used as a capacitor gate material.
In the embedding of the contact hole and via hole of the above described techniques, Al (aluminum), W (tungsten) or an alloy mainly containing Al or W is generally used. If such a metal or alloy directly contacts an underlying Si (silicon) substrate or Al wiring, there is the possibility that an alloy of both metals is formed due to the Si-suction effect of Al (counter diffusion) in the boundary portion between the metals. The alloy thus formed has a large value of resistance, so that the formation of such an alloy is not preferred from the point of view of the decrease of power consumption and high speed operation which are recently required for devices.
In addition, when W or a W alloy is used as an embedded layer for a contact hole, WF
6
gas used for forming the embedded layer tends to react with silicon of the substrate to deteriorate electrical characteristics to obtain undesired results.
Therefore, in order to prevent these disadvantages, before an embedded layer is formed in a contact hole or a via hole, a barrier layer is formed on the inner walls thereof, and the embedded layer is formed thereon. In this case, as the barrier layer, a double layer structure of a Ti (titanium) film and a TiN (titanium nitride) film is generally used.
Conventionally, such a barrier layer is deposited using a physical vapor deposition (PVD). Recently, the scale down and high density integration of devices are particularly required, and the design rule is particularly severe. In accordance therewith, the line width and the diameter of holes further decrease and the aspect ratio increases. As a result, the embedding performance of the PVD film is bad, so that it is not possible to ensure a sufficient contact resistance.
Therefore, the Ti film and TiN film constituting the barrier layer are deposited by a chemical vapor deposition (CVD) capable of expecting to form a better quality of film. When the Ti film is deposited by the CVD , TiCl
4
(titanium tetrachloride) and H
2
(hydrogen) are used as reaction gases to be activated as plasma to deposit the film. When the TiN film is deposited, TiCl
4
and NH
3
(ammonia) or MMH (monomethyl hydrazine) are used as reaction gases.
On the other hand, as described above, with the high density integration, a high dielectric material, such as Ta
2
O
5
, is used as a capacitor gate material in order to obtain a high capacitance without changing scale. However, such a high dielectric material is not more stable than SiO
2
which has been conventionally used as a capacitor gate material. Therefore, when a polysilicon, which has been conventionally used as a top electrode, is used, it is oxidized by heat history after the preparation of a capacitor, so that it is impossible to form a stable device. Therefore, TiN or the like, which is more difficult to be oxidized, is required as a top electrode.
Also in the case of this technique, the TiN film or the like has been conventionally deposited by the above described PVD. However, a recent highly integrated capacitor type, which requires a high coverage, e.g., a crown type, a fin type, or a RUG polysilicon, which has irreguralities formed on a polysilicon layer in order to increase the capacity of a capacitor when the crown type or fin type is formed, can not be deposited as a top electrode.
Therefore, a TiN film constituting a capacitor top electrode is also deposited by a CVD which is expected to be capable of forming a better quality of film at a high coverage. Also in this case, TiCl
4
and NH
3
or MMH are used as reaction gases for depositing the TiN film.
By the way, when a Tin film is thus deposited by the CVD, Cl (chlorine) remains in the film, so that the deposited film has a high specific resistance. If the specific resistance is so high, it is not possible to obtain sufficient characteristics when it is applied to a capacitor top electrode. In addition, the formed film is a high stress film. Moreover, the TiN film, which is a columnar crystal, has a low barrier characteristic since intergranular diffusion is easy to occur therein. In particular, the low barrier characteristic causes problems when the TiN film is used as a barrier layer for a Cu (copper) wiring or when the TiN film is used as an oxygen diffusion barrier, on the occasion of forming a Ta
2
O
5
capacitor top electrode. That is, the corrosion of the Cu wiring due to the remaining chlorine and the decrease of the capacity of Ta
2
O
5
due to the diffusion of O (oxygen), which increases the thickness of the Ta
2
O
5
film, cause problems.
SUMMARY OF THE INVENTION
The inventor has found that a TiN-series thin film, which is deposited by a CVD and which contains Ti, O and N (nitride), has a higher barrier characteristic than that of a conventional TiN film, and is suitable for a barrier layer. In addition, the inventor has found that a TiN-series thin film, which is deposited by a CVD and which contains Ti, N and P (phosphorus), has a lower resistance than that of a conventional TiN film, and is suitable for a barrier layer and a capacitor top electrode. Moreover, the inventor has found that the TiN-series thin film simultaneously containing O and P having the above described functions has both of a high barrier characteristic and a low resistance characteristic.
It is therefore an object of the present invention to provide a method for depositing a high-quality metallic nitride series, typically TiN-series, thin film having a higher barrier characteristic and/or a lower resistance than those of a conventional TiN film formed by a CVD.
The present invention also relates to a method for producing a film structure including such a metallic nitride series thin film.
Therefore, there is provided a method for depositing a TiN-series thin film, said method comprising the steps of: arranging a substrate in a process vessel; evacuating said process vessel, while heating said substrate; pre-heating said substrate while introducing a N
2
gas and a NH
3
gas into said process vessel; pre-flowing a TiCl
4
gas and an O-containing gas, without introducing same into said process vessel; and introducing said TiCl
4
gas, said N
2
gas, said NH
3
gas and said O-containing gas into said process vessel to form a thin film containing Ti, O and N on said substrate by a CVD, wherein flow rates of said gases in said pre-flowing step are equal to those in said introducing step.
There is also provided a method for depositing a TiN-series thin film, said method comprising the steps of: arranging a substrate in a process vessel; evacuating said process vessel, while heating said substrate; pre-heating said substrate while introducing a N
2
gas and a NH
3
gas into said process vessel; pre-flowing a TiCl
4
gas, an O-containing gas and a PH
3
gas, without introducing same into said process vessel; and introducing said TiCl
4
gas, said N
2
gas, said NH
3
gas, said O-containing gas and said PH
3
gas into said process vessel to form a thin film containing Ti, O, N and P on s
Meeks Timothy
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
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