Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
2000-09-21
2002-08-13
Chen, Bret (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S576000, C118S7230ER
Reexamination Certificate
active
06432493
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a plasma-enhanced chemical vapor deposition (PECVD) apparatus to be used for forming a thin film in a process of fabricating a semiconductor device, and more particularly to a plasma-enhanced chemical vapor deposition apparatus capable of uniformly forming a metal film having a high barrier characteristic.
2. Description of the Related Art
In these days, a design-rule in a semiconductor device is leveled up from a half-micron level to a quarter-micron level as LSI has been fabricated in a smaller size and in higher integration. In addition, techniques of forming a multi-layered wiring structure and planarizing a surface of a device makes an aspect ratio of a contact hole for connecting upper and lower wiring layers with each other higher and higher. In order to form a highly reliable multi-layered wiring structure including such a contact hole having a high aspect ratio, various methods have been used. For instance, one of such methods includes the steps of forming a titanium nitride layer acting as a barrier metal, conformal to a wiring layer for preventing diffusion of material of which the wiring layer is composed, forming an aluminum film, and thermally treating the aluminum film into fluid to thereby flow the fluidized aluminum into a contact hole. Another method includes the step of filling a contact hole with material of which an upper wiring layer is composed or a contact plug by selective chemical vapor deposition or blanket chemical vapor deposition of tungsten.
A titanium layer and a titanium nitride layer are formed generally by sputtering or reactive sputtering wherein titanium is used as a target material. Improvement has been made in these methods in order to fulfill a demand of forming a contact hole having a higher aspect ratio. That is, there have been suggested improvements in sputtering such as collimated sputtering wherein a vertical component of movement of particles obtained by sputtering is enhanced, and long throw sputtering wherein a vertical component of movement of particles obtained by sputtering by spacing a target from a substrate.
However, as an aspect ratio of a contact hole becomes higher and higher, it is difficult to form a thin film sufficiently at a bottom of a contact hole even in accordance with any one of the above-mentioned methods. In addition, in accordance with any one of the above-mentioned methods, a film is deposited at an opening of a contact hole in an over-hang shape, which exerts a harmful influence on a subsequent step of forming a wiring layer, and reduces reliability of a wiring layer formed on such a contact hole. Furthermore, any one of the above-mentioned sputtering provides a quite low film deposition rate, which reduces productivity of a thin film to be formed on a semiconductor substrate.
In order to solve the above-mentioned step coverage in sputtering, there has been suggested a plasma-enhanced chemical vapor deposition wherein a thin film is grown on a semiconductor substrate with the semiconductor substrate being heated, for instance, by J. T. Hillman et al., “Titanium Chemical Vapor Deposition”, VLSI Multilevel Interconnection Conference, pp. 365-367, 1994. In the suggested plasma-enhanced chemical vapor deposition, a titanium tetrachloride gas is employed as a process gas, and a titanium layer is formed by hydrogen reduction in a parallel plate type plasma-enhanced chemical vapor deposition apparatus. A titanium nitride film is formed conformal to a semiconductor substrate through the use of reduced pressure chemical vapor deposition.
FIG. 1
illustrates a typical conventional apparatus for carrying out plasma-enhanced chemical vapor deposition. The illustrated apparatus includes a reaction chamber
11
having an inlet port
11
a
through which a process gas is introduced into the reaction chamber
11
, and a pair of outlet ports
11
b
through which an exhausted gas is discharged, a susceptor
12
composed of metal for placing a semiconductor substrate
13
such as a silicon substrate thereon, an electrode
14
located in facing relation with the susceptor
12
and cooperating with the susceptor
12
to generate plasma
15
therebetween for forming a thin film on the semiconductor substrate
13
placed on the susceptor
12
, and an AC voltage source
16
for providing AC voltage to the electrode
14
for generating the plasma
15
between the susceptor
12
and the electrode
14
.
However, in the conventional plasma-enhanced chemical vapor deposition apparatus illustrated in
FIG. 1
, since there occurs an expansion in gas plasma-enhanced chemical vapor deposition. The illustrated apparatus includes a reaction distribution when the plasma
15
is generated, and a portion of the susceptor
12
which is not covered with the semiconductor substrate
13
is exposed to the plasma
15
, it is quite difficult or impossible to control a temperature of the susceptor
12
. As a result, portions of the susceptor
12
have different temperatures, which causes poor uniformity of a thin metal formed by plasma-enhanced chemical vapor deposition on the semiconductor substrate
13
, and also causes portions of the thus formed thin film to have different electric characteristics.
Furthermore, since a titanium nitride film has a polycrystalline structure including columnar crystals, a titanium nitride film formed as a barrier metal by means of the conventional plasma-enhanced chemical vapor deposition apparatus illustrated in
FIG. 1
would include a lot of crystal grains, and resultingly have a low barrier characteristic.
As another example, Japanese Unexamined Patent Publication No. 59-92520 has suggested a chemical vapor deposition apparatus including a cylindrical inner bell jar having an inner shape similar to an outer shape of an electrode situated in a reaction chamber. The bell jar is designed to be axially movable relative to the electrode.
As still another example, Japanese Unexamined Patent Publication No. 7-226378 has suggested a plasma-enhanced chemical vapor deposition apparatus including a bell jar composed of silicon nitride and located above a semiconductor substrate. A titanium/titanium nitride film is successively formed in the apparatus by employing a mixture gas of TiCl
4
and H
2
and a mixture gas of TiCl
4
, H
2
, and N
2
.
The chemical vapor deposition apparatuses suggested in the above-mentioned Publications are accompanied with the same problems as mentioned above. That is, portions of a susceptor have different temperatures, which causes poor uniformity of a thin metal, and also causes portions of the thin film to have different electric characteristics. Furthermore, a titanium nitride film formed by means of the suggested chemical vapor deposition apparatuses would include a lot of crystal grains, and resultingly have a low barrier characteristic.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a plasma-enhanced chemical vapor deposition apparatus capable of enhancing uniformity in a thin film formed on a semiconductor substrate, and of improving an electric characteristic of a thin film to be used as a barrier film.
It is also an object of the present invention to provide a method of carrying out plasma-enhanced chemical vapor deposition capable of doing the same.
In one aspect of the invention, there is provided a plasma-enhanced chemical vapor deposition apparatus including (a) a reaction chamber into which a process gas is introduced and from which an exhausted gas is discharged, (b) a susceptor having a first region on which a semiconductor substrate is to be placed and a second region other than the first region, (c) an electrode located in facing relation with the susceptor and cooperating with the susceptor to generate plasma therebetween for forming a thin film on the semiconductor substrate placed on the first region of the susceptor, and (d) a ceramics insulator located between the second region of the susceptor and the plasma.
There is still further provided a plasma-enhanced chemi
Chen Bret
Hayes & Soloway P.C.
NEC Corporation
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