Bubbler

Details Bubbler Bubbler

2000-09-20

2002-07-23

Paik, Sang (Department: 3742)

Electric resistance heating devices

Heating devices

Vaporizer

C118S724000

Reexamination Certificate

active

06424800

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bubbler for vaporizing a precursor for thin film deposition.
2. Description of the Related Art
In metal-organic chemical vapor deposition (MOCVD) processes, a precursor (source) for thin film deposition is vaporized in a bubbler and then carried along with carrier gas into a reaction chamber. Here, the amount of precursor supplied into the reaction chamber is influenced by parameters including the bubbler's temperature and pressure and the flow rate of the carrier gas. Thus, such parameters that determine the amount of precursor exhausted from the bubbler must be accurately controlled to deposit a thin film to a desired thickness.
FIG. 1
is a sectional view of a conventional bubbler for use in vaporizing a liquid source. The bubbler shown in
FIG. 1
has a carrier-gas inlet tube
12
, which is immersed in the liquid source
14
in a container
11
, and an exhaust tube
13
set above the surface of the liquid source
14
. A carrier gas
15
supplied through the carrier-gas inlet tube
12
forms bubbles, and the liquid source
14
is carried by a stream of carrier-gas bubbles through the exhaust tube
13
. The carrier gas
15
in the form of bubbles increases the contact area with the liquid source
14
, and thus this vaporization technique has the advantage of high source supply efficiency. However, the vaporization efficiency of the above bubbler is low when a less vaporizable source is used. Thus, the sources which can be used in the bubbler are limited.
To account for this problem, another bubbler as shown in
FIG. 2
was suggested. The conventional bubbler of
FIG. 2
includes a porous plate
28
, which is positioned at the middle of a vaporizer chamber
21
to enhance the vaporization efficiency of a less vaporizable source, and a heater
27
, which is installed close to the outer wall of the vaporizer chamber
21
to heat the vaporizer chamber
21
. In the bubbler, a liquid source supplied through a source inlet tube
22
is vaporized while passing through the porous plate
28
heated by the heater
27
, and exhausted through an exhaust tube
26
, along with a carrier gas supplied through a carrier-gas inlet tube
23
. The vaporization efficiency thus can be improved. However, there are problems in that the temperature distribution in the vaporizer chamber
21
varies according to the proximity to the heater
27
, and the vaporization efficiency of the source is nonuniform over the porous plate
28
.
Another drawback of the bubbler shown in
FIG.1
is found when a solid source is applied to the bubbler. Referring to
FIG. 3
, as a carrier gas
35
is supplied through the carrier-gas inlet tube
12
into a solid source
34
in the container
11
, the carrier gas
35
forms a gas tunnel
36
while carrying the solid source
34
. Here, the width and depth of the gas tunnel
36
are enlarged over time with use of the bubbler. Also, as the size of the gas tunnel
36
increases, the amount of solid source
34
carried by the carrier gas
35
varies, so that the amount of source supplied into a reaction chamber (not shown) cannot be accurately controlled. In addition, if the gas tunnel
36
is enlarged too much to carry the solid source
34
, the bubbler must be replaced by new one although a considerable amount of solid source
34
yet remains in the container
11
. Thus, there is a problem of waste of source.
Another example of a bubbler for solid sources is shown in FIG.
4
. The conventional bubbler of
FIG. 4
has a compressing plate
47
seated on a solid source
44
contained in a vaporizer chamber
41
, and a porous plate
48
on which the solid source
44
is put. An exhaust tube
43
is connected to the top of the vaporizer chamber
41
, separated a predetermined distance from the compressing plate
47
, and a porous filter
49
is fitted to the exhaust tube
43
so as to prevent leakage of the unvaporized solid source. A carrier-gas inlet tube
42
is connected to the vaporizer chamber
41
near the bottom thereof. In the bubbler, a carrier gas supplied through the carrier-gas inlet tube
42
enters the solid source
44
through the porous plate
48
, which allows uniform and wide contact between the solid source
44
and the carrier gas. However, the bubbler also fails to effectively vaporize less vaporizable sources, such as Sr(thd)
2
and Ba(thd)
2
. Thus, the applicable sources are limited.
SUMMARY OF THE INVENTION
It is a feature of the present invention to provide a bubbler capable of controlling the amount of source being vaporized therein with improved vaporization efficiency, and thus to loosen the limitation of applicable sources.
In accordance with one aspect of the present invention, there is provided a bubbler including a vaporizer chamber, the vaporizer chamber having defined therein a source inlet hole, an exhaust hole and a carrier gas inlet hole; a source supply unit connected to the source inlet hole; a plate installed in the vaporizer chamber, the plate being adapted to receive a source entering into the vaporizer chamber; and a heater source installed in the vaporizer chamber, the heater source being adapted to evenly heat the plate.
Preferably, the heater source has an area that is larger than the area of the facing porous plate, and the plate is a porous plate having pores capable of capturing the source. Preferably, the bubbler further comprises source diffusing means disposed in the vaporizer chamber, for causing the source to uniformly diffuse into the plate.
Other features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.


REFERENCES:
patent: 4770630 (1988-09-01), Akimoto et al.
patent: 5421895 (1995-06-01), Tsubouchi et al.
patent: 5580822 (1996-12-01), Hayakawa et al.
patent: 5651827 (1997-07-01), Aoyama et al.
patent: 6058926 (2000-05-01), Ruiz
patent: 11092941 (1999-04-01), None

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