MOCVD system

Details MOCVD system MOCVD system

2000-07-24

2001-11-20

Bueker, Richard (Department: 1763)

Coating apparatus

Gas or vapor deposition

Multizone chamber

C118S724000, C118S726000

Reexamination Certificate

active

06319327

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-212874, filed Jul. 27, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an MOCVD (Metal Organic Chemical Vapor Deposition) system used in semiconductor processes, and particularly to a system for forming a metal oxide film, such as a tantalum oxide (Ta
2
O
5
) film, on a target substrate, while using as a liquid raw material a metal organic compound that is in a liquid phase at room temperature (about 20° C.). The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD (Liquid Crystal Display) substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
In order to manufacture semiconductor devices, film formation and pattern etching are repeatedly applied to a semiconductor wafer. As semiconductor devices are increasingly highly miniaturized and integrated, demands on film formation become more strict. For example, very thin insulating films, such as capacitor insulating films and gate insulating films are still required to be thinner and to be more insulating.
Conventionally, silicon oxide films and silicon nitride films are used as the insulating films. In recent years, however, it has been proposed to form the insulating films from materials having more excellent insulating properties, such as metal oxides, e.g., tantalum oxide (Ta
2
O
5
), or high-dielectric or ferroelectric bodies containing two metal elements or more, e.g., (Ba,Sr)TiO
3
, i.e., BST. These films can be formed by means of MOCVD, i.e., using vaporized metal organic compounds.
Jpn. Pat. Appln. KOKAI Publication No. 2-283029 discloses an MOCVD technique for forming a tantalum oxide film. In the technique disclosed in this publication, a metal (tantalum) alkoxide, such as Ta(OC
2
H
5
)
5
(pentoethoxytantalum) is used as a liquid raw material. The liquid raw material is made to bubble by e.g., nitrogen gas, and is supplied to a process chamber preset to have a vacuum atmosphere. The supplied raw material is decomposed to offer a film forming material on the surface of a semiconductor wafer W heated to a process temperature of, e.g., 400° C. With this film forming material, a tantalum oxide (Ta
2
O
5
) film is formed on the surface of the semiconductor wafer W by means of deposition.
In this system, however, it is difficult to control the supply rate of the raw material with a high accuracy. This is because the liquid raw material is supplied by means of bubbling, and thus the flow rate of the liquid raw material is hardly accurately controlled. As a result, the supply rate of the raw material finally supplied to the process chamber shifts from the target value, thereby lowering reproducibility in the film thickness and quality of a formed CVD film.
Jpn. Pat. Appln. KOKAI Publication No. 10-79378 discloses another MOCVD technique for forming a tantalum oxide film, developed in light of the above described problem. In the technique disclosed in this publication, a liquid raw material the same as that of the former publication is delivered by the pressure of an inactive gas. The liquid raw material is supplied, while its flow rate is being controlled, and then is vaporized and turned into a process gas. The process gas is supplied to a process chamber and used for forming a CVD film on a semiconductor wafer.
FIG. 5
is a structural diagram schematically showing a conventional MOCVD system disclosed in the KOKAI Publication No. 10-79378.
In this system, a liquid raw material
4
, such as pentoethoxytantalum, is stored in a raw material tank
2
and is delivered by the pressure of a pressurized gas, such as He gas. The stored liquid raw material
4
is heated by a heater
6
to a temperature of, e.g., from 20 to 50° C., at which the liquid raw material
4
can easily flow. The delivered liquid raw material
4
flows downstream, while its flow rate is being controlled by a flow control unit
8
, and then is vaporized and turned into a process gas by an inactive gas, such as He gas, in a vaporizing unit
10
.
The process gas flows in a gas supply line
14
, which is wrapped by, e.g., a tape heater
12
for preventing the process gas from being turned back to liquid, and enters a film-forming unit
16
. The process gas is supplied from a showerhead
19
into a process chamber
18
, and then is decomposed to offer a film forming material on the surface of a semiconductor wafer W heated to a process temperature. With this film forming material, a tantalum oxide film is formed on the surface of the semiconductor wafer W by means of deposition.
The system of the KOKAI Publication No. 10-79378 can control the supply rate of the raw material more accurately than the former system. Depending on a situation, sometimes the latter system still lowers reproducibility in the film thickness and quality of a formed CVD film, sometimes as the case may be. Furthermore, the system includes heated members, such as the vaporizing unit
10
, pipes, and so forth, other than the process chamber
18
, and thus thermally influences the ambient environment.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an MOCVD system, which can offer a high reproducibility in the film thickness and quality of a formed CVD film.
Another object of the present invention is to provide an MOCVD system, which less thermally influences the ambient environment, but can offer a high reproducibility in the film thickness and quality of a formed CVD film.
According to a first aspect of the present invention, there is provided an MOCVD system for forming a metal oxide film on a target substrate, while using as a liquid raw material a metal organic compound that is in a liquid phase at room temperature:
an airtight process chamber;
a support member disposed in the process chamber and configured to support the target substrate;
an exhaust mechanism configured to exhaust the process chamber and set the process chamber to have a vacuum atmosphere;
a downstream main line connected to the process chamber and configured to supply a process gas thereto;
a vaporizing unit connected to the downstream main line outside the process chamber, and configured to heat the liquid raw material to a temperature higher than a vaporizing temperature of the liquid raw material and turn the liquid raw material into the process gas;
an upstream main line connected to the vaporizing unit and configured to supply the liquid raw material thereto;
a raw material tank connected to the upstream main line outside the process chamber and configured to store the liquid raw material;
a flow control unit arranged on the upstream main line between the raw material tank and the vaporizing unit; and
a temperature maintaining mechanism configured to maintain the raw material tank and the flow control unit at a temperature, which is lower than the vaporizing temperature and higher than the room temperature.
According to a second aspect of the present invention, there is provided an MOCVD system installed inside a clean room, for forming a metal oxide film on a target substrate, while using as a liquid raw material a metal organic compound that is in a liquid phase at room temperature:
an airtight process chamber;
a support member disposed in the process chamber and configured to support the target substrate;
an exhaust mechanism configured to exhaust the process chamber and set the process chamber to have a vacuum atmosphere;
a downstream main line connected to the process chamber and configured to supply a process gas thereto;
a vaporizing unit connected to the downstream main line outside the process chamber, and configu

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