Methods of cleaning vaporization surfaces

Details Methods of cleaning vaporization surfaces Methods of cleaning vaporization surfaces

2001-08-21

2004-09-28

Chen, Bret (Department: 1762)

Cleaning and liquid contact with solids

Processes

Including application of electrical radiant or wave energy...

C134S001200, C438S905000, C216S067000, C216S071000

Reexamination Certificate

active

06796313

ABSTRACT:

TECHNICAL FIELD
The invention pertains to methods of vaporizing materials, and to methods of cleaning vaporization surfaces. In further aspects, the invention encompasses vapor forming devices comprising plasma generation circuitry configured to utilize a vaporization surface as a plasma electrode.
BACKGROUND OF THE INVENTION
Vapor forming apparatuses have many applications in modern semiconductor processing. Among the applications is utilization in chemical vapor deposition apparatuses. An exemplary chemical vapor deposition apparatus
10
is described with reference to FIG.
1
. Apparatus
10
comprises a reaction chamber
12
having a substrate holder
14
contained therein. A substrate
16
is shown supported by substrate holder
14
. Substrate
16
can comprise, for example, a semiconductive material wafer, such as, for example, a wafer of monocrystalline silicon.
Chamber
12
has a vapor inlet
18
extending therethrough and a vapor outlet
19
also extending therethrough. Accordingly, a vapor (illustrated by arrows
20
) can be flowed through chamber
12
.
Chamber
12
can comprise one or more temperature control mechanisms (not shown) which can include, for example, heaters, or cooling gas flow ports. The thermal controls can enable substrate
16
to be maintained in a temperature such that a material is deposited onto substrate
16
from the vapor
20
within chamber
12
.
A vapor forming device
30
is provided to generate vapor
20
. Device
30
comprises an inlet region
32
configured to enable flow of a non-vapor state material
33
into device
30
. Device
30
further comprises an inlet port
34
configured to enable flow of a carrier gas
35
into device
30
. Additionally, device
30
comprises an outlet port
36
configured to enable vapor-state-material
20
to be output from device
30
and into reaction chamber
12
of apparatus
10
.
A vaporizer
40
is within device
30
and supported by a holder
42
. Vaporizer
40
comprises a surface
44
which can be referred to as a vaporization surface. Vaporizer
40
can comprise a heated material such that non-vapor-state-material
33
is converted from a non-vapor-state to a vapor-state upon contacting vaporization surface
44
.
Material
33
is typically initially in the form of a liquid, and is flowed into device
30
from a holding reservoir
46
. Although in the shown exemplary embodiment only one non-vapor-state material
33
is flowed into device
30
, it is to be understood that a plurality of different non-vapor-state materials can be flowed simultaneously into device
30
to form a vapor
20
comprising a composite of vapors from the various materials. An exemplary application in which a plurality of non-vapor-state materials are flowed into device
30
is a chemical vapor deposition process for formation of barium strontium titanate (BST).
Two separate configurations of prior art vaporizer devices
30
are described with reference to
FIGS. 2 and 3
.
Referring first to
FIG. 2
, a first prior art vaporization device
30
is illustrated in diagrammatic, schematic view. Such device comprises a COVA device (COVA Technologies, Inc., 2260 Executive Circle, Colorado Springs, Colo. 80906).
The vaporization device
30
FIG. 2
comprises vaporizer
40
which includes a pillar
60
extending upwardly into the device. Holder
42
, to the extent there is one in the device of
FIG. 2
, is defined by a bottom portion of pillar
60
. The device
30
of
FIG. 2
further includes a thermally conductive material
50
defining a void
52
therein. Material
50
is shaped to define an outer periphery
54
comprising sides
56
and ends
58
. Material
50
is further configured to form pillar
60
, which protrudes upwardly from one of the ends
58
and into a region between sides
56
. The outlet region
36
and inlet region
34
of the device of
FIG. 2
extend through material
50
to define gas passageways into and out of void region
52
.
Non-vapor-state-material inlet
32
comprises three separate capillaries (
32
a
,
32
b
, and
32
c
) extending through an end
58
and terminating above pillar region
60
. Non-vapor-state material
33
comprises three separate materials (
33
a
,
33
b
and
33
c
), which can comprise, for example, liquids.
In operation, material
50
is heated and non-vapor state materials
33
a
,
33
b
and
33
c
are flowed through inlets
32
a
,
32
b
and
32
c
and onto pillar region
60
. The non-vapor state materials are then vaporized upon contact with a heated vaporization surface of pillar region
60
to form a vapor
20
. Such vapor
20
then flows to outlet
36
and out of device
30
. The three materials
33
a
,
33
b
and
33
c
can comprise, for example, Ba(THD)
2
, Sr(THD)
2
, and Ti(O-iPr)
2
(THD)
2
, in, for example, applications wherein a vapor is to be formed for deposition of BST. In the above formulas, THD stands for bis(2,2,6,6-tetramethyl-3,5heptanedionate) (C
11
H
19
O
2
), and O-iPr stands for isopropoxide (C
3
H
7
O).
In the above-described application for forming BST, material
50
and pillar region
60
are preferably heated to a temperature of about 250° C. (Ba(THD)
2
vaporizes at about 212° C.). Also, the carrier gas
35
preferably comprises a temperature of about 250° C. Carrier gas
35
can comprise, for example, nitrogen or helium.
A second prior art vaporization device
30
is described with reference to FIG.
3
. In the device of
FIG. 3
, vaporizer
40
comprises a heated frit, and holder
42
comprises a pair of projections extending from sides of frit
40
. The embodiment of
FIG. 3
further comprises an outer periphery
70
surrounding frit
40
and defining a void
72
therein. Inlet region
32
comprises three separate capillaries (labeled as
32
a
,
32
b
and
32
c
) which extend through periphery
70
and into void regions
72
. Capillaries
32
a
,
32
b
and
32
c
are configured such that non-vapor-state-materials
33
a
,
33
b
and
33
c
flow through capillaries
32
a
,
32
b
and
32
c
and onto a vaporization surface
44
of frit
40
.
In operation, frit
40
is heated to a temperature such that materials
33
a
,
33
b
and
33
c
are vaporized upon contact with surface
44
to form a vapor
20
which exits device
30
through outlet port
36
. Also, a carrier gas
35
is injected into device
30
through inlet port
34
to flow vapor
20
out of device
30
. Materials
33
a
,
33
b
and
33
c
can comprise, for example, Ba(THD)
2
, Sr(THD)
2
, and Ti(O-iPr)
2
(THD)
2
, for formation of BST. In such embodiments, frit
40
is preferably heated to a temperature of about 250° C., and carrier gas
35
is also preferably heated to a temperature of about 250° C. The system described with reference to
FIG. 3
is a diagrammatic, schematic view of an Advanced Delivery and Chemical Systems vaporizer. (Advanced Delivery and Chemical Systems (ADCS), 7
Commerce Drive, Danbury Conn.
06810-4169.)
A problem with the prior art devices described above is that materials injected into the devices can decompose to form deposits on vaporization surfaces
44
. A reason that the deposits form can be, for example, that the vaporization temperature is close to a decomposition temperature for non-vapor-state-materials
33
injected into devices
30
. The deposits can decrease the effectiveness of vaporization surfaces
44
, and can, for example, cause clogging and other problems due to particulate formation. Accordingly, it would be desirable to develop methods for cleaning deposits from surfaces
44
.
SUMMARY OF THE INVENTION
In one aspect, the invention encompasses a method of utilizing a vaporization surface as an electrode to form a plasma within a vapor forming device.
In another aspect, the invention encompasses a method of chemical vapor deposition. A vaporization surface is provided and heated. At least one material is flowed past the heated surface to vaporize the material. A deposit forms on the vaporization surface during the vaporization. The vaporization surface is then utilized as an electrode to form a plasma, and at least a portion of the deposit is remo

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