U.S. patent application number 10/147851 was filed with the patent office on 2003-10-30 for apparatus and method for supplying cesium using injector.
This patent application is currently assigned to Filteray Fiber Optics, Inc.. Invention is credited to Kim, Daesig.
Application Number | 20030201586 10/147851 |
Document ID | / |
Family ID | 29244804 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030201586 |
Kind Code |
A1 |
Kim, Daesig |
October 30, 2003 |
Apparatus and method for supplying cesium using injector
Abstract
An apparatus and method for supplying cesium by using an
injector is disclosed in the present invention, which increases
vaporization efficiency and stably supplies cesium gas for a long
period of time. The apparatus includes a mass flow controller
controlling an amount of an externally introduced inert gas, a
pre-heater pre-heating the inert gas introduced through a first gas
flow tube from the mass flow controller, a cesium storage unit
emitting cesium by using a pressure gas supplied through a pressure
gas supplying tube, an injector emitting the cesium supplied from
the cesium storage unit, and a cesium vaporizer vaporizing the
cesium emitted from the injector and emitting the inert gas
introduced from the pre-heater through a second gas flow tube along
with the cesium gas through a third gas flow tube. It is emphasized
that this abstract is provided to comply with the rules requiring
an abstract that will allow a searcher or other reader to quickly
ascertain the subject matter of the technical disclosure. It is
submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims.
Inventors: |
Kim, Daesig; (Pleasanton,
CA) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
Filteray Fiber Optics, Inc.
|
Family ID: |
29244804 |
Appl. No.: |
10/147851 |
Filed: |
May 20, 2002 |
Current U.S.
Class: |
266/217 |
Current CPC
Class: |
C23C 16/4481 20130101;
C23C 14/228 20130101; H01J 7/20 20130101 |
Class at
Publication: |
266/217 |
International
Class: |
C22B 026/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2002 |
KR |
P2002-0023379 |
Claims
What is claimed is:
1. An apparatus for supplying cesium by using an injector,
comprising: a mass flow controller controlling an amount of an
externally introduced inert gas; a pre-heater pre-heating the inert
gas introduced through a first gas flow tube from the mass flow
controller; a cesium storage unit emitting cesium by using a
pressure gas supplied through a pressure gas supplying tube; an
injector emitting the cesium supplied from the cesium storage unit;
and a cesium vaporizer vaporizing the cesium emitted from the
injector and emitting the inert gas introduced from the pre-heater
through a second gas flow tube along with the cesium gas through a
third gas flow tube.
2. The apparatus according to claim 1, wherein the injector is
controlled by externally applied pulse signals.
3. The apparatus according to claim 1, wherein the injector
regulates a size of a cesium particle, an amount of cesium, and an
area of cesium spray.
4. The apparatus according to claim 1, wherein the inert gas
includes one of argon, nitrogen, and helium.
5. The apparatus according to claim 1, wherein the cesium storage
unit is filled with liquid cesium.
6. The apparatus according to claim 1, wherein an inside of the
cesium storage unit is maintained at a temperature of at least
29.degree. C.
7. The apparatus according to claim 1, wherein the cesium vaporizer
is maintained at a temperature ranging from about 200 to
300.degree. C.
8. The apparatus according to claim 1, wherein the pressure gas is
formed of an inert gas.
9. The apparatus according to claim 8, wherein the inert gas is
formed of nitrogen.
10. The apparatus according to claim 1, further comprising a heater
heating the pre-heater, the cesium storage unit, and the cesium
vaporizer.
11. The apparatus according to claim 1, further including a
plurality of heating wires heating the first, second, and third gas
flow tubes.
12. The apparatus according to claim 1, further including a valve
installed within both the second and third gas flow tubes in order
to control an amount of cesium flowing therein.
13. The apparatus according to claim 1, further including a
pressure gas regulator regulating an amount of pressure gas
introduced to the cesium storage unit.
14. The method for supplying cesium by using an injector,
comprising: controlling an amount of an externally introduced inert
gas; pre-heating the inert gas; emitting and vaporizing cesium
supplied by a pressure gas; and emitting the vaporized cesium along
with the pre-heated inert gas.
15. The method according to claim 14, wherein the cesium in the
emitting and vaporizing cesium supplied by a pressure gas is
emitted on a regular basis.
16. The method according to claim 14, wherein an amount of the
pressure gas in the emitting and vaporizing cesium supplied by a
pressure gas is controlled in order to regulate an amount of cesium
to be emitted.
Description
[0001] This application claims the benefit of the Korean
Application No. P2002-23379 filed on Apr. 29, 2002, which is hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an apparatus and method for
supplying cesium (Cs), and more particularly, to an apparatus and
method for supplying cesium using an injector, which increases
vaporization efficiency of cesium and enables a continuous supply
of cesium gas for a long period of time.
[0004] 2. Discussion of the Related Art
[0005] Generally, an ion source is used in ion injection, sputter
deposition, ion beam deposition, and ion spectroscopy. More
specifically, when sufficient amount of cesium ions exists on the
surface of the substrate to be processed, the cesium ions decrease
the work function of the surface of the substrate. This is because
cesium has a low electron affinity. Therefore, the cesium existing
on the surface of the substrate increases an amount of the negative
ion emission.
[0006] Under the atmospheric pressure, cesium has a liquid point of
28.degree. C. and a boiling point of 690.degree. C. At 100.degree.
C., cesium has a vapor pressure of 10E-4 Torr.
[0007] However, cesium is easily oxidized when it is exposed to
oxygen. Moreover, cesium explodes when it is brought into contact
with humidity. Therefore, vapor pressure of cesium cannot be
controlled easily, which results in many limitations in the
application of cesium.
[0008] A related art apparatus for supplying cesium will be
described with reference to the accompanying drawings.
[0009] FIG. 1 illustrates a schematic view of the related art
apparatus for supplying cesium using solid electrolyte, which is
disclosed in U.S. Pat. No. 5,521,389.
[0010] As shown in FIG. 1, the related art apparatus for supplying
cesium using solid electrolyte includes an ion pellet 11 having a
cesium compound in the form of an oxide sealed therein, an ion
emitter 12 emitting cesium ions from the cesium compound inside the
ion pellet 11 when brought into contact with metal, and a heater 13
heating the ion pellet 11 so that cesium ions can be emitted
through the ion emitter 12.
[0011] The related art apparatus for supplying cesium also includes
a heat cutoff layer (not shown), which is made of one of molybdenum
and tantalum and formed on an outer surface of the heater 13 in
order to prevent heat produced from the heater 13 to be radiated to
the outside. An anode electrode (not shown) for an electrical
connection of the ion pellet 11 and a metal tube (not shown)
preventing the cesium compound from flowing out of the ion pellet
11 are also included in the apparatus.
[0012] Herein, the ion emitter 12 is a porous electrode coated with
tungsten on a side surface of the ion pellet 11. Also, the heater
13 formed on the circumference of the ion pellet is made of a
filament coated with alumina.
[0013] As described above, in the related art apparatus for
supplying cesium using solid electrolyte, the solid electrolyte
including cesium emits cesium ions at an elevated temperature
ranging from 900 to 1000.degree. C. For an effective emission of
the electrodes, the temperature should be maintained at least at
1000.degree. C.
[0014] Due to a limited amount of solid electrolyte sealed within
the ion pellet 11, this type of cesium source is not desirable for
a long-term use. Particularly, ion beam flux is limited. Therefore,
it is difficult to carry out a deposition process on a wide
surface.
[0015] In addition, when the ion pellet 11 is used under an oxygen
environment for a long period of time, an oxide layer is formed on
the porous ion emitter 12 due to oxidation of cesium, which results
in an instability in the discharged amount of cesium ions.
Therefore, in order to accurately control the discharged amount of
cesium ions, an apparatus that can control the heating of the ion
pellet 11 by measuring the discharged amount is required. When
using the apparatus for supplying cesium in a physical vapor
deposition process, cesium produced by a high temperature heating
process is only diffused by a thermal kinetic movement of gas
within a vacuum. Therefore, the flux cannot be controlled.
[0016] FIG. 2 illustrates a schematic view of an apparatus for
supplying cesium using a refractory metal ribbon, which is
disclosed in U.S. Pat. No. 5,466,941. This structure resolves the
problems caused in the apparatus for supplying cesium using solid
electrolyte.
[0017] As shown in FIG. 2, the apparatus for supplying cesium using
a refractory metal ribbon includes an extraction electrode pair 21,
a refractory metal ribbon 22 ionizing the cesium discharged from
the extraction electrode 21, and an electrode for forming a beam
(not shown) formed on the upper and lower portions of the
refractory metal ribbon 22 in order to form the positively charged
and ionized cesium ions into a beam.
[0018] A heater (not shown) controlling vapor pressure used for
discharging non-ionized cesium to the refractory metal ribbon 22 is
also included in the apparatus. Herein, the refractory metal ribbon
is formed of tungsten.
[0019] However, in the apparatus for supplying cesium using a
refractory metal ribbon with the above structure, the extraction
electrode 21 must be heated at an elevated temperature ranging from
300 to 400.degree. C. in order to discharge non-ionized cesium.
Furthermore, the refractory metal ribbon 22 must be heated at an
elevated temperature of 1200.degree. C. in order to positively
charge the discharged cesium.
SUMMARY OF THE INVENTION
[0020] Accordingly, the present invention is directed to an
apparatus and method for supplying cesium using an injector that
substantially obviates one or more of problems due to limitations
and disadvantages of the related art.
[0021] Another object of the present invention is to provide an
apparatus and method for supplying cesium using an injector whereby
cesium vaporization efficiency is increased in order to provide a
larger amount of cesium gas.
[0022] Another object of the present invention is to provide an
apparatus and method for supplying cesium using an injector, which
prevents the cesium from being oxidized or deteriorated, thereby
allowing a stable supply of cesium for a long period of time.
[0023] A further object of the present invention is to provide an
apparatus and method for supplying cesium using an injector, which
can control the supplied amount of cesium with precision.
[0024] Additional features and advantages of the invention will be
set forth in the description which follows and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0025] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, an apparatus for supplying cesium by using an injector
includes a mass flow controller controlling an amount of an
externally introduced inert gas, a pre-heater pre-heating the inert
gas introduced through a first gas flow tube from the mass flow
controller, a cesium storage unit emitting cesium by using a
pressure gas supplied through a pressure gas supplying tube, an
injector emitting the cesium supplied from the cesium storage unit,
and a cesium vaporizer vaporizing the cesium emitted from the
injector and emitting the inert gas introduced from the pre-heater
through a second gas flow tube along with the cesium gas through a
third gas flow tube.
[0026] Herein, externally applied pulse signals allow the injector
to emit liquid cesium on a regular basis. The injector also
controls the size of a cesium particle, the amount of cesium, and
the level of spray.
[0027] In another aspect of the present invention, a method of
supplying cesium by using an injector includes controlling an
amount of an externally introduced inert gas, pre-heating the inert
gas, emitting and vaporizing cesium supplied by a pressure gas, and
emitting the vaporized cesium along with the pre-heated inert
gas.
[0028] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiments of
the invention and together with the description serve to explain
the principle of the invention.
[0030] In the drawings:
[0031] FIG. 1 illustrates a schematic view of a related art
apparatus for supplying cesium using solid electrolyte;
[0032] FIG. 2 illustrates a schematic view of a related art
apparatus for supplying cesium using a refractory metal ribbon;
and
[0033] FIG. 3 illustrates a schematic view of an apparatus for
supplying cesium according to the present invention.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0034] Reference will now be made in detail to the illustrated
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0035] FIG. 3 illustrates a schematic view of an apparatus for
supplying cesium according to the present invention.
[0036] As shown in FIG. 3, the apparatus for supplying cesium by
using an injector includes a mass flow controller (MFC) 31
controlling an amount of an externally introduced inert gas, a
pre-heater 34 pre-heating the inert gas introduced through a first
gas flow tube 32 from the mass flow controller (MFC) 31 and
emitting the pre-heated inert gas through a second gas flow tube
33, a cesium storage unit 36 emitting cesium by using a pressure
gas supplied through a pressure gas supplying tube 35, an injector
37 emitting the cesium supplied from the cesium storage unit 36,
and a cesium vaporizer 39 vaporizing the cesium emitted from the
injector 37 and emitting the inert gas introduced from the
pre-heater 34 through the second gas flow tube 33 along with the
cesium gas through a third gas flow tube 38.
[0037] In addition, the apparatus for supplying cesium by using an
injector according to the present invention further includes a
heater 40 heating the pre-heater 34, the cesium storage unit 36,
and the cesium vaporizer 39, a plurality of heating wires heating
the first, second, and third gas flow tubes 32, 33, and 38, a first
cutoff valve 41 installed within the second gas flow tube 33 and
supplying and cutting off the inert gas introduced to the cesium
vaporizer, 39 from the pre-heater 34, and a second cutoff valve 42
installed within the third gas flow tube 38 and supplying and
cutting off the cesium gas supplied to a deposition device 43 from
the cesium vaporizer 39, and a pressure gas regulator (not shown)
installed within the pressure gas supplying tube 35 and controlling
the amount of pressure gas introduced to the cesium storage unit
36.
[0038] Herein, a two-stage pressure regulator is used as the
pressure gas regulator. A tube 44 connects the cesium storage unit
36 and the injector 37. A heating wire may also be formed on the
circumference of the tube 44 in a similar manner as the first,
second, and third gas flow tubes 32, 33, and 38.
[0039] In addition to argon (Ar), nitrogen (N.sub.2) and helium
(He) may also be used as an inert gas. The inert gas may also be
used as a pressure gas supplied to the cesium storage unit 36. The
cesium storage unit 36, which is filled with liquid cesium, may be
maintained at a temperature of at least 29.degree. C. in order to
maintain the cesium in a liquid phase.
[0040] The injector 37 is controlled by pulse signals applied by an
external controlling device, wherein an emitter within the injector
37 repeatedly opens and closes so as to emit liquid cesium on a
regular basis.
[0041] The apparatus for supplying cesium is not only applicable to
a physical vapor deposition system, but also to any vapor
deposition system using ion beam, a chemical mechanical vapor
deposition system, a display device of an electronic tube a camera
tube, an electronic microscope, and a photoelectron generator.
[0042] The operation of the above-described apparatus for supplying
cesium of the present invention will now be explained.
[0043] The mass flow controller 31 controls the amount of the
externally introduced inert gas. The heater 40 installed on the
circumference of the pre-heater 34 pre-heats the inert gas
introduced to the pre-heater 34 through the first gas flow tube
32.
[0044] A pressure gas is supplied to the cesium storage unit 36,
which is filled with liquid cesium. At this point, the pressure gas
supplied through the pressure gas supplying tube 35 emits the
liquid cesium with the cesium storage unit 36 to the outside. More
specifically, pressure within the cesium storage unit 36 increases
as the pressure gas is introduced therein. The liquid cesium is
then sent to the injector 37 through a tube 44.
[0045] Herein, the amount of liquid cesium sent to the injector 37
from the cesium storage unit 36 may vary according to the amount of
pressure gas, which is regulated by the pressure gas regulator.
[0046] The injector 37 receiving cesium from the cesium storage
unit 36 periodically emits cesium into the cesium vaporizer 39 in
accordance with pulse signals generated from an external power
supply. Herein, the shape and size of the emitter within the
injector determine the size of a cesium particle, the amount of
cesium, and the area of cesium spray. Therefore, in order to obtain
a desired amount of cesium and area of cesium spray, an adequate
size and shape should be selected for the emitter in the
injector.
[0047] When the fine particles of cesium are emitted from the
injector 37 reach the inner surface of the heated cesium vaporizer
39, the cesium is vaporized by an instantaneous heating process.
Due to the instantaneous vaporization of cesium, the pressure
within the cesium vaporizer 39 increases instantaneously as well.
The degree of cesium vaporization increases in accordance with the
small size of the emitted cesium particles and the large area of
spray.
[0048] The vaporized cesium is then discharged through the third
gas flow tube 38 along with the pre-heated inert gas introduced
from the pre-heater 34, and finally supplied to the deposition
device 43.
[0049] Herein, the heater 40 heats the cesium vaporizer 39 to a
temperature ranging from about 200 to 300.degree. C. and vaporizes
the cesium. The heating wires maintain the first, second, and third
gas flow tubes 32, 33, and 38 at about the same temperature as the
cesium vaporizer 39.
[0050] The above-described apparatus for supplying cesium according
to the present invention uses the pressure gas regulator to
regulate the amount of cesium supplied to the injector 37, thereby
regulating with precision the amount of cesium gas supplied to the
deposition device 43. Additionally, by vaporizing the fine
particles of the liquid cesium emitted from the injector 37,
vaporization efficiency of cesium may be enhanced.
[0051] More specifically, the emitted amount of cesium gas depends
highly on the amount of supplied cesium gas, more specifically, the
pressure of the pressure gas, the viscosity of cesium, and the
pulse signals of the injector, and the degree of cesium
vaporization. The degree of cesium vaporization relies on the size
of liquid cesium particles, the area of spray, and the heating
temperature.
[0052] In addition, the first, second, and third gas flow tubes 32,
33, and 38 are maintained at a high temperature, thereby preventing
clogging of the tubes caused by an oxidation of cesium. Thus, high
quality cesium gas may be supplied to a vacuum system (i.e., a
deposition device 43), thereby facilitating the production of
negatively charged ions on to a substrate to be treated.
[0053] Furthermore, cesium gas is supplied to the deposition device
along with the inert gas, which prevents the counter flow of oxygen
or other oxidizing substances therein. Thus, cesium can be used
stably for a long period of time without being deteriorated.
[0054] More specifically, in comparison with the related art, when
vaporizing cesium by using the apparatus for supplying cesium
according to the present invention, a larger amount of cesium gas
may be stably and continuously supplied for a long period of
time.
[0055] The above-described apparatus for supplying cesium according
to the present invention has the following advantages.
[0056] An injector emitting liquid cesium is installed within the
apparatus for supplying cesium in order to vaporize the fine cesium
particles, thereby increasing vaporization efficiency. Accordingly,
a large amount of cesium gas can be supplied to the deposition
device.
[0057] A pressure gas regulator regulates the amount of pressure
gas supplied to the cesium storage unit, which allows the
regulation of the amount of liquid cesium supplied to the injector.
The pulse signals control the degree of opening and closing of the
injector. As a result, the amount of cesium gas supplied to the
deposition device can be regulated.
[0058] A heater or a plurality of heating wires are installed, so
that the temperature of the entire system including a pre-heater, a
cesium vaporizer, and gas flow tubes is readily controlled and
maintained. Also, an inert gas is supplied to a deposition device
along with cesium gas, which prevents the cesium from being
oxidized. Thus, cesium gas may be stably supplied for a long period
of time without being deteriorated.
[0059] It will be apparent to those skilled in the art that various
modifications and variations can be made in the apparatus and
method for supplying cesium by using an injector of the present
invention without departing from the spirit or scope of the
inventions. Thus, it is intended that the present invention covers
the modifications and variations of this invention provided they
come within the scope of the appended claims and their
equivalents.
* * * * *