Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...
Reexamination Certificate
1998-07-22
2001-01-23
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
For metallic, siliceous, or calcareous basework, including...
C134S021000, C134S022100, C216S037000, C438S905000
Reexamination Certificate
active
06176936
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cleaning of a Chemical vapor Deposition (CVD) apparatus and more particularly, to an in-situ cleaning method of a reaction chamber of a CVD apparatus in which an elementary metal or metal compound film is formed on a semiconductor substrate or wafer through a chemical reaction of reducing decomposition of a metal halide gas.
2. Description of the Prior Art
In recent years, miniaturization of contact holes has been progressing more and more with the increasing integration level of Large-Scale Integrated circuits (LSIs) and consequently, the aspect ratio of the contact holes has been becoming larger and larger. Here, the aspect ratio is defined as a ratio of the depth of a contact hole with respect to the diameter thereof.
Under such the circumstance as above, the conventional wiring or interconnection film, which is typically made of aluminum (Al) deposited by a sputtering process, tends to have various disadvantages. For example, the contact resistance of the wiring or interconnection film becomes high and the wiring or interconnection film itself becomes discontinuous at the windows of the contact holes, which are due to the low step-coverage property of the film. Also, the Al film tends to be discontinuous due to the electromigration phenomenon during operation, thereby lowering its reliability.
To avoid these disadvantages, various metal plugs have been developed to electrically interconnect an upper conductive layer to a lower conductive layer. In this case, the upper and lower conductive layers are electrically connected together through the metal plugs that fill the contact holes of an intervening dielectric film between the upper and lower conductive layers.
A typical example of the metal plugs is tungsten (W) plugs formed by a plasma-enhanced CVD process with a good step coverage.
In the case of the W plugs, first, a thin titanium (Ti) film is formed on a dielectric film with contact holes by a sputtering process, so that the Ti film is deposited not only on the surface of the dielectric film but also in the contact holes thereof. The thin Ti film serves to lower the contact resistance with a silicon substrate as the lower conductive layer.
Next, a titanium nitride (TiN) film is formed by a sputtering process on the entire Ti film thus deposited. The TiN film serves to improve the adhesion strength of a W film to the Ti film and to prevent the W atoms in the W film from entering the silicon substrate. The Ti and TiN films serves as a metal barrier.
Subsequently, a W film for forming the W plugs is formed on the entire TiN film by a CVD process.
Finally, the unnecessary W, TiN, and Ti films on the surface of the dielectric film are etched back, thereby leaving selectively the W, TiN, and Ti films in the contact holes thereof. Thus, the W plugs located on the TiN and Ti films are formed in the respective contact holes of the dielectric film.
However, if the aspect ratio of the contact holes is further increased, the sputtered Ti and TiN films for the W plugs will become unable to have satisfactorily large thicknesses in the contact holes. This leads to such problems as increase in contact resistance and damage of the electronic devices or elements on the substrate.
To prevent these problems from occurring, the Ti and TiN films may be formed by CVD processes. In this case, however, the following problem tends to occur.
Specifically, if each of the Ti and TiN films is formed by a CVD process, the Ti or TiN films tends to be deposited not only on the substrate but also on the exposed inner surfaces of a reaction chamber of a CVD apparatus. The undesired Ti or TiN film that has been deposited on the inner surfaces of the chamber will be detached therefrom at the time when the Ti or TiN film has grown to have a specific thickness. The detached Ti or TiN film will become a cause of particulate contamination generated in the chamber. This problem will be explained in detail below with reference to
FIGS. 1A and 1B
.
FIGS. 1A and 1B
schematically show the typical configuration of a plasma-enhanced CVD apparatus.
A plasma-enhanced CVD apparatus
1100
shown in
FIGS. 1A and 1B
has a reaction chamber
1101
, an upper electrode
1102
fixed onto the inner top wall of the chamber
1101
, a susceptor or substrate holder
1103
fixed onto the inner bottom wall of the chamber
1101
, a radio-frequency (RF) power supply
1109
provided outside the chamber
1101
, a direct-current (DC) power supply
1104
provided outside the chamber
1101
, and a vacuum pump system
1114
provided outside the chamber
1101
.
The upper electrode
1102
, which is electrically connected to the RF power supply
1109
, has an inner space
1113
and emission holes
1102
a
. A specific RF power is supplied to the upper electrode
1102
on operation. The inner space
1113
communicates with gas sources (not shown) provided outside the chamber
1101
through a gas inlet
1106
of the reaction chamber
1101
. The emission holes
1102
a
communicates with a reaction space
1112
of the chamber
1101
. The supplied gasses to the inner space
1113
are mixed in the space
1113
and then, emitted through the emission holes
1102
a
to the reaction space
1112
.
The inside of the reaction chamber
1101
(i.e. the reaction space
1112
) communicates with the vacuum pump system
1114
through a gas outlet
1105
of the chamber
1101
. A pressure-regulating valve
1108
is provided at the gas outlet
1105
. The gas or gases existing in the reaction space
1112
is/are evacuated by the vacuum pump system
1114
to generate a vacuum atmosphere in the space
1112
. The pressure in the space
1112
may be adjusted by the pressure-regulating valve
1108
.
The susceptor
1103
is electrically connected to the DC power supply
1104
. A specific DC voltage is applied to the susceptor
1103
and the substrate
1107
placed thereon on operation.
When a Ti film is formed on a silicon wafer or substrate
1107
on which a lot of semiconductor devices have been fabricated through the popular fabrication processes such as photolithography, dry etching, and film deposition, first, the silicon substrate
1107
is transported into the reaction chamber
1101
of the CVD apparatus
1100
and then, placed on the susceptor
1103
. Prior to this step, a specific vacuum atmosphere has been generated in the reaction space
1112
of the chamber
1101
.
Next, titanium tetrachloride (TiCl
4
), argon (Ar), and hydrogen (H
2
) gasses are supplied to the inner space
1113
of the upper electrode
1102
through the gas inlet
1106
of the reaction chamber
1101
, and mixed therein. The mixture of TiCl
4
, Ar, and H
2
gases thus produced is then emitted toward the substrate
1107
through the emission holes
1102
a
of the upper electrode
1102
. Thus, the mixture of TiCl
4
, Ar, and H
2
gases are introduced into the reaction space
1102
of the chamber
1101
.
On the other hand, a specific DC bias voltage is applied to the substrate
1107
by the DC power supply
1104
and at the same time, a specific RF power is supplied to the upper electrode
102
by the RF power supply
1109
, thereby making a plasma
1111
of TiCl
4
, Ar, and H
2
in the reaction space
1102
of the chamber
1101
, as shown in FIG.
1
A.
Thus, a Ti film (not shown) with a thickness of approximately 5 to 30 nm is formed on the silicon substrate
1107
by a plasma-enhanced CVD process.
During this CVD process, undesired Ti films
1110
tend to be deposited on several areas of the inner walls of the vacuum chamber
1101
, the upper electrode
1102
, and the susceptor
1103
, as shown in FIG.
1
A. The undesired Ti films
1110
thus deposited will grow every time when the above CVD process is carried out.
If the undesired Ti films
1110
grows to have a specific thickness after the above CVD process is repeated approximately a hundred times in the plasma CVD apparatus shown in
FIG. 1A
, at least a part of the undesired Ti films
1110
tend to be detached from the chamber
1101
, the upper elec
Gulakowski Randy
NEC Corporation
Olsen Allan
Sughrue Mion Zinn Macpeak & Seas, PLLC
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