U.S. patent application number 11/993795 was filed with the patent office on 2010-09-09 for apparatus and process for integrated gas blending.
This patent application is currently assigned to ADVANCED TECHNOLOGY MATERIALS, INC.. Invention is credited to Jose I. Arno, Jeffrey J. Homan, Joseph D. Sweeney.
Application Number | 20100224264 11/993795 |
Document ID | / |
Family ID | 37595829 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100224264 |
Kind Code |
A1 |
Homan; Jeffrey J. ; et
al. |
September 9, 2010 |
APPARATUS AND PROCESS FOR INTEGRATED GAS BLENDING
Abstract
A system (10) for delivery of dilute fluid, utilizing an active
fluid source (12), a diluent fluid source (14), a fluid flow
metering device (24) for dispensing of one of the active and
diluent fluids, a mixer (28) arranged to mix the active and diluent
fluids to form a diluted active fluid mixture, and a monitor (42)
arranged to sense concentration of active fluid and/or diluent
fluid in the diluted active fluid mixture, and responsively adjust
the fluid flow metering device (24) to achieve a predetermined
concentration of active fluid in the diluted active fluid mixture.
A pressure controller (38) is arranged to control flow of the other
of the active and diluent fluids so as to maintain a predetermined
pressure of the diluted active fluid mixture dispensed from the
system. The fluid dispensed from the system then can be adjustably
controlled by a flow rate controller, e.g., a mass flow controller,
to provide a desired flow to a fluid-utilizing unit, such as a
semiconductor process tool. An end point monitoring assembly is
also described, for switching fluid sources (12, 15) to maintain
continuity of delivery of the diluted active fluid mixture.
Inventors: |
Homan; Jeffrey J.; (Ladson,
SC) ; Arno; Jose I.; (Brookfield, CT) ;
Sweeney; Joseph D.; (Winsted, CT) |
Correspondence
Address: |
INTELLECTUAL PROPERTY / TECHNOLOGY LAW
PO BOX 14329
RESEARCH TRIANGLE PARK
NC
27709
US
|
Assignee: |
ADVANCED TECHNOLOGY MATERIALS,
INC.
Danbury
CT
|
Family ID: |
37595829 |
Appl. No.: |
11/993795 |
Filed: |
June 22, 2006 |
PCT Filed: |
June 22, 2006 |
PCT NO: |
PCT/US06/24308 |
371 Date: |
April 29, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60693015 |
Jun 22, 2005 |
|
|
|
Current U.S.
Class: |
137/93 ;
137/602 |
Current CPC
Class: |
F17C 2250/032 20130101;
F17C 2225/0123 20130101; F17C 5/06 20130101; F17C 2221/03 20130101;
F17C 2250/043 20130101; F17C 2265/025 20130101; B01F 15/00285
20130101; F17C 2250/0452 20130101; F17C 2227/0157 20130101; G05D
11/132 20130101; F17C 13/025 20130101; F17C 2223/0123 20130101;
Y10T 137/87571 20150401; F17C 2250/0626 20130101; F17C 2221/01
20130101; F17C 2223/035 20130101; B01F 15/0429 20130101; F17C
2250/0443 20130101; Y10T 137/2509 20150401; H01L 21/2225 20130101;
F17C 2270/0518 20130101; B01F 15/00207 20130101; F17C 13/02
20130101; B01F 15/0022 20130101; F17C 2225/035 20130101; F17C 7/02
20130101; B01F 3/028 20130101; F17C 2250/0447 20130101 |
Class at
Publication: |
137/93 ;
137/602 |
International
Class: |
G05D 11/00 20060101
G05D011/00; A23G 9/28 20060101 A23G009/28 |
Claims
1-101. (canceled)
102. A system adapted for coupling with (i) an active fluid source
of active fluid and (ii) a diluent fluid source of diluent fluid,
and adapted for delivery of dilute fluid, the system including: a
fluid flow metering device adapted to dispense one of the active
and diluent fluids; a mixer arranged to mix the active and diluent
fluids to form a diluted active fluid mixture; a monitor arranged
to sense concentration of any of the active fluid and the diluent
fluid in the diluted active fluid mixture; a controller arranged to
receive from the monitor a signal indicative of concentration of
the active fluid and/or the diluent fluid in the diluted active
fluid mixture, and to responsively adjust the fluid flow metering
device to achieve a predetermined concentration of active fluid in
the diluted active fluid mixture; and a pressure controller
disposed upstream of the mixer, arranged to sense and control
pressure of the other of the active and diluent fluids, and
configured to maintain at the mixer a predetermined pressure of
said other of the active and diluent fluids.
103. The system of claim 102, wherein the fluid flow metering
device is arranged for dispensing the active fluid.
104. The system of claim 102, wherein the pressure controller is
arranged to control diluent fluid flow.
105. The system of claim 102, wherein the monitor is arranged to
sense concentration of the diluent fluid in the diluted active
fluid mixture.
106. The system of claim 102, wherein the pressure controller is
arranged to control active fluid flow.
107. The system of claim 102, coupled with a fluid-utilizing unit
comprising a semiconductor or microelectronic device manufacturing
tool, for flow of diluted active fluid mixture thereto.
108. The system of claim 107, further comprising a flow controller
disposed downstream of the mixer and arranged to provide a
predetermined flow of diluted active fluid mixture to the
fluid-utilizing unit.
109. The system of claim 107, wherein the semiconductor or
microelectronic device manufacturing tool comprises any of an ion
implantation tool, a chemical vapor deposition tool, an epitaxial
doping tool, and an etching tool.
110. The system of claim 102, wherein the monitor is adapted to
sense any of arsine, phosphine, hydrogen, nitrogen trifluoride,
ammonia, nitrous oxide, tungsten hexafluoride, hydrogen chloride,
chlorine, hydrogen bromide, diborane, methane, methane, ethylene,
chloroform, propane, butane, sulfur hexafluoride, nitrogen,
fluorine, ammonium fluoride, ammonium phosphate, ammonium
hydroxide, boron trifluoride, boron trichloride, dichlorosilane,
germane, tetrafluoromethane, trifluoromethane, difluoromethane,
methyl fluoride, hexafluoroethane, pentafluoromethane,
perfluoropropane, octafluorocyclobutane, nitric oxide, silane,
silicon tetrachloride, silicon tetrafluoride, trichlorosilane,
hydrogen selenide, and organometallic reagent gases.
111. The system of claim 102, wherein the monitor comprises a
thermopile infrared analyzer.
112. The system of claim 102, wherein the monitor comprises a fluid
monitoring device selected from the group consisting of
spectrometric, spectroscopic, electrochemical, acoustic, thermal,
photometric, chromatographic, colorimetric, surface acoustic wave
(SAW), photonic and flame ionizer fluid monitors.
113. The system of claim 102, wherein the fluid flow metering
device comprises a device selected from the group consisting of
mass flow controllers, micro-valves actuatable for dispensing low
flow rates of active fluid from the active fluid source, and
flowmeters coupled with flow control valves.
114. The system of claim 102, wherein the fluid flow metering
device comprises an electrically-responsive variable restricted
flow orifice.
115. The system of claim 102, wherein the fluid flow metering
device comprises an electrically controlled variable restrictive
flow orifice, said monitor is arranged to detect a control signal
transmitted to the electrically-controlled variable restrictive
flow orifice, and said monitor is arranged to responsively disable
a source associated with said one of the active and diluent fluids
when said electrical signal is at a value indicative of exhaustion
or near-exhaustion of said source associated with said one of the
active and diluent fluids.
116. The system of claim 102, further comprising said active fluid
source including a gas storage and dispensing vessel containing any
of (A) a physical adsorbent medium sorptively retaining active gas,
and from which active gas is desorbed for dispensing of active gas
from the vessel; and (B) an interiorly disposed regulator for
dispensing of active gas from the vessel at a pressure determined
by set point of the regulator.
117. A method for delivery of dilute fluid utilizing an active
fluid source containing active fluid and a diluent fluid source
containing diluent fluid, the method comprising: controllably
dispensing one of the active fluid and diluent fluid from its
associated fluid source at predetermined flow rate to a mixer;
dispensing to the mixer the other of the active fluid and diluent
fluid from its associated fluid source, including sensing and
controlling pressure of said other of the active and diluent fluid
to maintain at the mixer a predetermined pressure of said other of
the active and diluent fluid; mixing the dispensed active fluid
with dispensed diluent fluid in the mixer, to form a diluted active
fluid mixture; monitoring concentration of at least one of the
active and diluent fluids in the diluted active fluid mixture; and
responsively adjusting the dispensing rate of the fluid dispensed
at predetermined flow rate, to maintain a predetermined
concentration of active fluid in the diluted active fluid mixture;
and dispensing the diluted active fluid mixture for use in a
fluid-utilizing process.
118. The method of claim 117, wherein said use comprises
manufacturing a semiconductor product.
119. The method of claim 117, wherein the active fluid source
comprises a fluid storage and dispensing vessel containing any of
(1) a physical adsorbent medium having sorptive affinity for the
active fluid and (2) a fluid pressure regulator.
120. The method of claim 117, wherein said monitoring comprises use
of a device selected from the group consisting of spectrometric,
spectroscopic, electrochemical, acoustic, thermal, photometric,
chromatographic, colorimetric, surface acoustic wave (SAW),
photonic and flame ionizer fluid monitors.
121. The method of claim 117, wherein said concentration monitoring
comprises use of a thermopile infrared detector.
122. The method of claim 117, wherein said controllable dispensing
is performed with a variable flow control device, the method
further comprising monitoring a characteristic of the variable flow
control device and responsively terminating the blending of any of
said active and diluent fluids when the monitored characteristic is
indicative of approaching exhaustion of said active fluid source or
diluent fluid source
123. A system adapted for coupling with (a) an active fluid source
of active fluid and (b) a diluent fluid source of diluent fluid,
and for delivery of dilute fluid, the system including: a fluid
flow metering device for dispensing of one of the active and
diluent fluids; a mixer arranged to mix the active and diluent
fluids to form a diluted active fluid mixture; a monitor arranged
to sense concentration of any of active fluid and diluent fluid in
the diluted active fluid mixture; a controller arranged to receive
from the monitor a signal indicative of concentration of any of
active fluid and diluent fluid in the diluted active fluid mixture,
and responsively adjust the fluid flow metering device to achieve a
predetermined concentration of active fluid in the diluted active
fluid mixture; and at least one of: (I) a pressure controller
disposed upstream of the mixer, arranged to sense and control
pressure of the other of the active and diluent fluids, and
configured to maintain at the mixer a predetermined pressure of
said other of the active and diluent fluids; and (II) an end point
detector assembly arranged to determine when at least one of the
active fluid source and diluent fluid source is empty or
approaching an empty or near-empty condition, and to responsively
disable such fluid source(s) from fluid dispensing.
124. The system of claim 123, wherein the fluid flow metering
device comprises an electrically-responsive variable restrictive
flow orifice, and the end point detector assembly is arranged to
monitor an electrical signal transmitted to the variable
restrictive flow orifice, and to responsively terminate dispensing
of at least one of the active fluid and diluting fluid.
125. The system of claim 123, comprising both (I) and (II).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to apparatus and method for
supplying dilute gases at predetermined concentrations, e.g., as
source gas for ion implantation doping of semiconductor or other
microelectronic device materials.
[0003] 2. Description of the Related Art
[0004] The semiconductor industry uses a wide variety of dilute
gases in applications where the source material is highly toxic or
hazardous and the dosage of active gas species is small.
[0005] For instance, ion implantation doping of epitaxial films by
requires source gases such as arsine, phosphine, and germane in
highly dilute states. As an example, arsenic may be implanted in a
semiconductor film for doping thereof, from a dilute
arsine/hydrogen gas mixture. In such arsenic doping application, a
source gas of low arsine content e.g., 50 parts per million (ppm)
may be further diluted with hydrogen to achieve a desired
hydrogen/arsine gas mixture. The flows of the dilute arsine
starting material and the diluent hydrogen that is added thereto to
form the final dilute arsine gas mixture can be controlled by mass
flow controllers, to deliver a metered amount of the final diluted
arsine to the ionizer unit of the ion implant system.
[0006] Generally, two primary approaches are utilized in the
semiconductor industry for supplying an active gas (such term being
used hereinafter to designate the gas component of interest, such
as the dopant gas species) in diluted form in a gas mixture useful
for a desired application.
[0007] A first category of dilute gas supply techniques utilizes
pre-mixed high-pressure gas mixtures (containing the
low-concentration active gas component) as the source gas medium,
as dispensed for use from high-pressure gas supply vessels such as
pressurized gas cylinders. This gas supply approach has the
following deficiencies: [0008] (1) the gas supply vessels are
exhausted at a high rate, requiring numerous change-outs of the gas
supply vessels during the operation of the active gas-consuming
process; [0009] (2) when gas supply vessels are changed out as they
are exhausted, the active gas-consuming process may need to be
re-qualified, since the concentration of active gas supplied from a
freshly installed gas supply vessel may be different from the
concentration dispensed from a previously installed gas supply
vessel; [0010] (3) in addition to deficiency (2), the gas
concentration of the active gas dispensed from any given gas supply
vessel is fixed by the gas supply vessel manufacturer, and there is
no capability of delivering varying concentrations depending on
time-varying conditions in the downstream active gas-consuming
process; [0011] (4) the concentration of the active gas in the gas
mixture stored in the gas supply vessel can change with time due to
decomposition of the active gas component, or the concentration of
the active gas can vary with successive change-outs of gas supply
vessels, in an unknown and unexpected manner, and [0012] (5) the
gas supply vessel typically is at high atmospheric pressure to
maximize inventory of the active gas in the vessel, entailing a
potentially unsafe situation if the gas supply vessel ruptures or
leakage from the associated head assembly, valves, etc. of the
vessel occurs.
[0013] The second general category of dilute gas supply techniques
involves in-situ generation of gas, using solids or liquid raw
materials to generate the desired gas species through chemical
reaction. In-situ gas generation has the following associated
deficiencies: [0014] (1) the time required to initiate gas
generation and achieve steady-state gas production is generally
substantial and does not permit a quick-response turn-on of gas
dispensing to be achieved; [0015] (2) the raw materials used as
reactants for in-situ gas generation are frequently highly toxic in
character, thereby raising safety and operational issues; [0016]
(3) in-situ gas generators are typically relatively complex
systems, including for example, gas generation chambers, reactant
supplies, reactant flow circuitry (since even in the case of solid
reactant sources, there is typically a fluid co-reactant),
dispensing lines, and associated in-line filters, purifiers,
interlocks, etc.; [0017] (4) in-situ gas generators as
conventionally employed involve consumable parts requiring periodic
replacement, e.g., filters and purifiers; and [0018] (5) in-situ
gas generation systems are relatively expensive, both in capital
expenditure and in overall cost of ownership.
[0019] U.S. Pat. No. 7,063,097 issued Jun. 20, 2006 to Jose I. Arno
and James A. Dietz for "In-Situ Gas Blending and Dilution System
for Delivery of Dilute Gas at a Predetermined Concentration"
describes an in-situ gas blending and dilution system for delivery
of dilute gas at a predetermined concentration, which includes an
active gas source and a diluent gas source. A gas flow-metering
device is provided for dispensing the active gas at a predetermined
flow rate. A gas blender mixer is arranged to mix (i) active gas
from the active gas source that is dispensed at the predetermined
flow rate by the gas flow-metering device, with (ii) diluent gas,
to form a diluted active gas mixture. The system further includes a
monitor arranged to sense concentration of active gas in the
diluted active gas mixture and to responsively adjust the gas
flow-metering device, to control the dispensing rate of the active
gas, and maintain a predetermined concentration of active gas in
the diluted active gas mixture.
[0020] In one embodiment of the system described in U.S. Pat. No.
7,063,097, as adapted for delivery of gas for ion implantation in a
semiconductor manufacturing facility, the monitor includes a
thermopile infrared (TPIR) detector, and the system utilizes a
variable restricted flow orifice (RFO) as a flow control device for
the source gas, and a mass flow controller (MFC) as a flow control
device for the diluent gas, with a micro-pump to deliver a specific
concentration of the source gas to the semiconductor manufacturing
ion implant tool from the gas blender.
[0021] In such ion implantation system, it is desirable to be able
to control the overall flow of the diluted gas mixture that is
entering the ion implant tool from the gas blender. This is
problematic, however, since any adjustment of the flow rate causes
the pressure maintained inside the gas blender to change. This in
turn disrupts the gas concentration signal that is being sensed by
the TPIR detector, since the signal sensed by the TPIR detector is
directly proportional to both temperature and pressure. Any change
in pressure causes the calibration of the TPIR to be inaccurate,
with the result that an incorrect concentration of the source gas
in the diluted mixture is caused to be fed to the semiconductor
manufacturing tool.
[0022] Additionally, in such ion implantation system, if the
blender is operated at extremely low pressures, e.g., at less than
50 torr, the TPIR detector may be unable to sense any level of
source gas.
[0023] This inability to accurately control concentration under
adjusted flow rates, and potential inability to sense diluted
source gas concentration at very low pressures, present significant
operating issues.
[0024] The active gas source used in gas blender delivery systems
of the type discussed above can include fluid storage and
dispensing packages in which a physical adsorbent retains the
active gas thereon in a vessel, for desorption of the active gas
and discharge from the vessel under dispensing conditions. Such gas
supply systems are commercially available from ATMI, Inc., Danbury,
Conn., USA under the trademarks SDS and SAGE and are described, for
example, in U.S. Pat. Nos. 5,518,528; 5,704,965; 5,704,967; and
5,707,424.
[0025] The active gas source used in the gas blender delivery
system alternatively can include a fluid storage and dispensing
package in which a pressure regulator is positioned in the interior
volume of a vessel holding the active fluid under pressure. The
pressure regulator is arranged with a set point permitting
dispensing of gas deriving from the fluid, at pressure determined
by the set point, e.g., a subatmospheric pressure providing a high
level of safety in operation. Internal regulator gas supply
packages of such type are commercially available from ATMI, Inc.,
Danbury, Conn., USA under the trademark VAC and are described, for
example, in U.S. Pat. Nos. 6,101,816 and 6,089,027.
[0026] In the use of the above-mentioned SDS, SAGE and VAC packages
for supply of active gas in the above-described gas blender
delivery systems, it frequently is unclear to the user when the gas
storage and dispensing package is approaching exhaustion. As a
result of such uncertainty, the package may be taken out of service
at a premature point in time, relative to the actual point of
exhaustion, with consequent waste of residual active gas remaining
in the package and adverse effect on the economics of the process
using the active gas. Alternatively, the package may continue to be
operated until total exhaustion of the active gas has occurred, and
the package is "running dry." As a result, the process being
serviced by the empty package must be stopped, to accommodate
change out of the gas supply package and introduction of a fresh
package of the active gas. This circumstance involves extended
down-time periods in the operation of the microelectronic product
manufacturing facility, with resulting adverse economic impact on
the facility.
[0027] Accordingly, the microelectronic product manufacturing
industry has continuing need for improved gas supply sources and
monitoring of gas-dispensing operations, for efficient and economic
delivery of dilute gases to process equipment.
SUMMARY OF THE INVENTION
[0028] The present invention relates to a system for delivery of
diluted fluid, e.g., to a fluid-utilizing unit such as an ion
implantation tool employed for manufacture of semiconductor devices
and integrated circuit structures, or other microelectronic device
manufacturing operation.
[0029] In one aspect, the present invention relates to a system for
delivery of dilute fluid, including:
an active fluid source; a diluent fluid source; a fluid flow
metering device for dispensing of one of the active and diluent
fluids; a mixer arranged to mix the active and diluent fluids to
form a diluted active fluid mixture; a monitor arranged to sense
concentration of active fluid and/or diluent fluid in the diluted
active fluid mixture, and responsively adjust the fluid flow
metering device to achieve a predetermined concentration of active
fluid in the diluted active fluid mixture; and a pressure
controller arranged to control flow of the other of the active and
diluent fluids so as to maintain a predetermined pressure of the
diluted active fluid mixture dispensed from the system.
[0030] In another aspect, the invention relates to a system for
delivery of dilute fluids, comprising:
an active fluid source; a diluent fluid source; a gas flow metering
device that is joined in fluid flow communication with the active
fluid source, and selectively adjustable to dispense active fluid
at predetermined flow rate; a pressure controller that is joined in
fluid flow communication with the diluent fluid source, and
arranged to dispense diluent fluid at predetermined pressure; a
mixer arranged to mix the dispensed active fluid at predetermined
flow rate with the dispensed diluent fluid at predetermined
pressure, to form a diluted active fluid mixture; and a monitor
arranged to (i) sense concentration of active fluid in the diluted
active fluid mixture prior to dispensing thereof from the system,
and (ii) responsively adjust the fluid flow metering device, to
control dispensing rate of the active fluid so as to maintain a
predetermined concentration of active fluid in the diluted active
fluid mixture dispensed from the system.
[0031] In another aspect, the invention relates to a fluid blender
apparatus, comprising:
flow circuitry arranged for connection to an active fluid source
and to a diluent fluid source; a fluid flow metering device that is
joined in fluid flow communication with the active fluid source
flow circuitry, and selectively adjustable to dispense active fluid
at predetermined flow rate; a pressure controller that is joined in
fluid flow communication with the diluent fluid source flow
circuitry, and arranged to dispense diluent fluid at predetermined
pressure; a mixer arranged to mix the dispensed active fluid at
predetermined flow rate with the dispensed diluent fluid at
predetermined pressure, to form a diluted active fluid mixture; and
a monitor arranged to (i) sense concentration of active fluid in
the diluted active fluid mixture prior to dispensing thereof from
the fluid blender apparatus, and (ii) responsively adjust the fluid
flow metering device, to control dispensing rate of the active
fluid so as to maintain a predetermined concentration of active
fluid in the diluted active fluid mixture dispensed from the fluid
blender apparatus; wherein the fluid flow metering device, pressure
controller, mixing device and monitor are contained in a fluid
blender box, and the flow circuitry is arranged for connection to
active fluid and diluent fluid sources located exterior of the
fluid blender box, and the diluted active fluid mixture is
dispensed to a site exterior of the box.
[0032] A still further aspect of the invention relates to an
apparatus for delivery of dilute fluid, wherein said apparatus is
adapted for coupling with an active fluid source and with a diluent
fluid source, to deliver the dilute fluid as a mixture of active
fluid from the active fluid source, and diluent fluid from the
diluent fluid source, such apparatus comprising:
a fluid flow metering device that is adapted to be joined in fluid
flow communication with the active fluid source, and selectively
adjustable to dispense active fluid at predetermined flow rate; a
pressure controller that is adapted to be joined in fluid flow
communication with the diluent fluid source, to dispense diluent
fluid at predetermined pressure; a mixer arranged to mix the
dispensed active fluid at predetermined flow rate with the
dispensed diluent fluid at predetermined pressure, to form a
diluted active fluid mixture; and a monitor arranged to (i) sense
concentration of active fluid in the diluted active fluid mixture
prior to dispensing of the diluted active fluid mixture, and (ii)
responsively adjust the fluid flow metering device, to control
dispensing rate of the active fluid so as to maintain a
predetermined concentration of active fluid in the dispensed
diluted active fluid mixture.
[0033] In various further aspects, the invention relates to methods
of delivering fluid, utilizing apparatus and systems of the
foregoing types.
[0034] Another aspect of the invention relates to a method for
delivery of dilute fluid, comprising:
providing an active fluid source and a diluent fluid source;
controllably dispensing one of the active fluid and diluent fluid
from its fluid source at predetermined flow rate; dispensing the
other of the active fluid and diluent fluid from its fluid source
at predetermined pressure; mixing dispensed active fluid with
dispensed diluent fluid, to form a diluted active fluid mixture;
monitoring concentration of at least one of the active and diluent
fluids in the diluted active fluid mixture, and responsively
adjusting the dispensing rate of the fluid dispensed at
predetermined flow rate, to maintain a predetermined concentration
of active fluid in the diluted active fluid mixture; and dispensing
the diluted active fluid mixture for use.
[0035] In yet another aspect, the invention relates to a method for
delivery of dilute fluid, comprising:
and providing an active fluid source and a diluent fluid source;
controllably dispensing active fluid from the active fluid source
at predetermined flow rate; dispensing diluent fluid from the
diluent fluid source at predetermined pressure; mixing active fluid
from the active fluid source that is dispensed at said
predetermined flow rate, with diluent fluid from the diluent fluid
source, to form a diluted active fluid mixture; monitoring
concentration of active fluid in the diluted active fluid mixture,
and responsively adjusting the dispensing rate of the active fluid,
to maintain a predetermined concentration of active fluid in the
diluted active fluid mixture; and dispensing the diluted active
fluid mixture for use.
[0036] A further aspect of the invention relates to a system for
delivery of dilute fluid, including:
[0037] an active fluid source;
[0038] a diluent fluid source;
[0039] a fluid flow metering device for dispensing of one of the
active and diluent fluids;
[0040] a mixer arranged to mix the active and diluent fluids to
form a diluted active fluid mixture;
[0041] a monitor arranged to sense concentration of active fluid
and/or diluent fluid in the diluted active fluid mixture, and
responsively adjust the fluid flow metering device to achieve a
predetermined concentration of active fluid in the diluted active
fluid mixture; and
[0042] at least one of:
[0043] (I) a pressure controller arranged to maintain a
predetermined pressure of the diluted active fluid mixture
dispensed from the system; and
[0044] (II) an end point detector assembly arranged to determine
when at least one of the active fluid source and diluent fluid
source is empty or approaching an empty or near-empty condition,
and to responsively disable such fluid source(s) from fluid
dispensing.
[0045] Another aspect of the invention relates to a method of
blending fluids to form a multicomponent fluid, said method
comprising monitoring the multicomponent fluid for concentration of
one or more of components thereof, and responsively modulating the
blending to maintain the concentration of said one or more
components at predetermined level(s) in the multicomponent fluid,
monitoring pressure of at least one of the blending fluids, and
responsively modulating the flow of at least one of the blending
fluids to maintain pressure of the multicomponent fluid at
predetermined level(s).
[0046] A still further aspect of the invention relates to a method
of making a microelectronic product, comprising use of the
multicomponent fluid prepared by the method of the preceding
paragraph.
[0047] Yet another aspect of the invention relates to a fluid
delivery assembly, including a monitor adapted to determine
concentration of one or more components of a multicomponent
fluid,
a controller operatively coupled to the monitor to respond to the
determined concentration and generate a correlative output, a flow
control device arranged to modulate flow of one or more components
of the multicomponent fluid in response to the correlative output,
a mixer arranged to mix components to form the multicomponent
fluid, and a pressure controller adapted to maintain predetermined
pressure of multicomponent fluid introduced to said monitor.
[0048] In another aspect, the invention relates to a
microelectronic product manufacturing facility comprising a fluid
delivery assembly as described herein.
[0049] Additional aspects of the invention relates to methods of
delivering fluid, and to methods of making microelectronic
products.
[0050] A further aspect of the invention relates to a method of
combining two or more fluids to form a multicomponent fluid
containing a predetermined concentration of one or more component
fluids therein, said method comprising blending said two or more
fluids with modulated addition of one or more but less than all of
said two or more fluids, wherein such addition is modulated in
response to concentration sensing of at least one of said one or
more but less than all of said two or more fluids, and controlling
pressure of the multicomponent fluid so that same is at
predetermined pressure. In lieu of, or addition to, pressure
control of the multicomponent fluid, other multicomponent fluid
parameters may be controlled in specific embodiments of the
invention, such as temperature, density, turbidity, etc.
[0051] Another aspect of the invention relates to a method of
manufacturing a microelectronic product, comprising use of a
multicomponent fluid as produced by the method of the preceding
paragraph.
[0052] A further aspect of the invention relates to a subassembly
coupleable with sources of active fluid and diluent fluid, for
blending thereof to deliver dilute fluid, such subassembly
including:
[0053] a fluid flow metering device adapted to dispense one of the
active and diluent fluids;
[0054] a mixer arranged to mix the active and diluent fluids to
form a diluted active fluid mixture;
[0055] a monitor arranged to sense concentration of the active
fluid and/or the diluent fluid in the diluted active fluid mixture,
and to responsively adjust the fluid flow metering device to
achieve a predetermined concentration of active fluid in the
diluted active fluid mixture; and
[0056] a pressure controller arranged to control flow of the other
of the active and diluent fluids so as to maintain a predetermined
pressure of the diluted active fluid mixture dispensed from the
system.
[0057] Other aspects, features and embodiments of the invention
will be more fully apparent from the ensuing disclosure and
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] FIG. 1 is a schematic representation of a gas delivery
system arranged to supply a dilute gas mixture to an ion
implantation semiconductor manufacturing tool.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0059] The disclosures of U.S. Pat. No. 6,909,973 issued Jun. 20,
2005 in the name of Jose I. Arno for "Photometrically Modulated
Delivery of Reagents," and U.S. Pat. No. 7,063,097 issued Jun. 20,
2006 in the names of Jose I. Arno, et al. for "In-Situ Gas Blending
and Dilution System for Delivery of Dilute Gas at a Predetermined
Concentration" are hereby incorporated herein by reference in their
entireties, for all purposes.
[0060] The present invention provides a system for delivery of
dilute fluid, utilizing an active fluid source, a diluent fluid
source, a fluid flow metering device for dispensing of one of the
active and diluent fluids, a mixer arranged to mix the active and
diluent fluids to form a diluted active fluid mixture, and a
monitor arranged to sense concentration of active fluid and/or
diluent fluid in the diluted active fluid mixture, and responsively
adjust the fluid flow metering device to achieve a predetermined
concentration of active fluid in the diluted active fluid mixture.
A pressure controller is arranged to control flow of the other of
the active and diluent fluids so as to maintain a predetermined
pressure of the diluted active fluid mixture dispensed from the
system. The fluid dispensed from the system then can be adjustably
controlled by a flow rate controller, e.g., a mass flow controller,
to provide a desired flow to a fluid-utilizing unit, such as a
semiconductor process tool. Semiconductor process tools useful for
such purpose can be of any suitable type, e.g., ion implantation
tools, chemical vapor deposition tools, epitaxial doping tools,
etching tools, etc.
[0061] In a specific embodiment, the invention includes an active
fluid source, a diluent fluid source, a fluid flow metering device
for dispensing of the active fluid, and a mixer, e.g., a mixing
device or a housing or chamber containing such device, or a portion
of the flow circuitry, or other apparatus or structure that is
arranged to mix the active fluid and the diluent fluid for forming
a diluted active fluid mixture. A monitor is arranged in this
embodiment to sense concentration of active fluid in the diluted
active fluid mixture, and responsively adjust the fluid flow
metering device for control of dispensing rate of the active fluid,
to achieve the predetermined concentration of active fluid in the
diluted active fluid mixture that is dispensed from the system. A
pressure controller is employed in this embodiment to control
diluent fluid flow so as to maintain a predetermined pressure of
the diluted active fluid mixture dispensed from the system.
[0062] The present invention provides a highly effective system and
method for supplying dilute gas at predetermined concentration,
e.g., as source gas for ion implantation doping of a semiconductor
material.
[0063] Additionally, the invention resolves a major problem
associated with the use of mass flow controllers for delivering
dilute gas, namely, the inability of mass flow controllers used in
wafer processing tools to accommodate significant deviations in
pressure. Such deficiency of mass flow controllers results in
inaccurate monitoring results when MFCs are utilized in streams
susceptible to variability in pressure, such as where the flow of
carrier gas is modulated to produce a desired concentration of an
active gas component in a mixed gas stream formed by combination of
the carrier gas with the active gas component.
[0064] In one specific embodiment, as hereinafter described in
greater detail, the fluid flow metering device includes a variable
RFO in a fluid flow line interconnecting the active fluid source
and a pump for flowing the active fluid to the mixer, the pressure
controller includes an electronic pressure controller and/or a
mechanical pressure controller disposed in a fluid flow line
interconnecting the diluent gas source and the mixer, the mixer
includes a static mixer, and the monitor comprises an in-line fluid
analyzer arranged to produce an output control signal correlative
to the sensed active fluid concentration in the diluted active
fluid mixture, with the control signal being transmitted to the
fluid flow metering device to modulate the set point thereof to
achieve a predetermined constant active fluid concentration for the
desired application of the diluted active fluid mixture.
[0065] The invention thereby provides a system for delivery of a
controlled pressure diluted fluid mixture including a dilute
component fluid at a selected concentration, whereby the user of
the dispensed fluid mixture can adjustably control the flow thereof
for the desired downstream use thereof at the desired concentration
of the dilute component fluid.
[0066] The fluid flow metering device can be of any suitable type,
including for example a variable RFO device, as discussed
illustratively above, or alternatively a mass flow controller, a
micro-valve element actuatable for dispensing very low flow rates
of the active fluid component from the active fluid supply, a
flowmeter coupled with a flow control valve in the dispensing line,
or any other element or assembly that is effective to provide a
selected flow rate of the active fluid from the active gas
source.
[0067] The fluid flow metering device in another embodiment
includes a fluid regulator element associated with a fluid storage
and dispensing vessel, e.g., of a type described in U.S. Pat. No.
6,089,027, wherein the fluid regulator element is operatively
coupled with a feedback control loop, arranged to achieve a desired
active gas concentration in the dispensed fluid mixture.
[0068] The active fluid source can be of any suitable type, e.g., a
gas storage and dispensing vessel or container holding the neat
active gas to be diluted for use. In one embodiment, the active
fluid source comprises a sub-atmospheric pressure active gas
storage and dispensing vessel of the type described in U.S. Pat.
No. 5,518,528 to Glenn M. Tom et al. and commercially available
from ATMI, Inc., Danbury, Conn., USA) under the trademark SDS,
wherein active gas is sorptively retained on a physical adsorbent
and selectively desorbed therefrom for dispensing of active gas
from the vessel. In another embodiment, the neat active fluid
source comprises a gas storage and dispensing vessel of the type
described in U.S. Pat. No. 6,089,027 to Luping Wang, et al. and
commercially available from ATMI, Inc. (Danbury, Conn.) under the
trademark VAC, featuring an interiorly disposed regulator element
for dispensing of the active gas at a pressure determined by the
regulator set point.
[0069] The active fluid source may alternatively be constituted
and/or arranged, in any suitable manner, e.g., as a supply
structure, material or operation. For example, the active fluid
source may include a solid physical adsorbent-based package of the
type described in U.S. Pat. No. 5,518,528 to Glenn M. Tom et al. In
other embodiments, the active fluid may be liberated from a liquid
solution, or be generated by an in-situ generator, or be generated
from a reactive liquid as described in U.S. Patent Publication No.
20040206241 published October, 2004 for "Reactive Liquid Based Gas
Storage and Delivery System," or be obtained from a reactive solid,
or from a vaporizable or sublimable solid. In general, any
appropriate source or supply of the active fluid can be used. In a
specific embodiment, the active fluid source includes a retention
structure, as described in U.S. Pat. No. 5,916,245 issued Jun. 29,
1999 for "High Capacity Gas Storage and Dispensing System."
[0070] The mixer arranged to mix the active fluid and the diluent
fluid for forming a diluted active fluid mixture can be of any
suitable type, whereby the active fluid and the diluent fluid are
intermixed with one another for discharge at a desired dilute
concentration of the active fluid, e.g., for flow to a downstream
dilute fluid mixture-utilizing process. The mixer can include a
dynamic mixing device such as for example a pump, compressor,
rotary mixer, or the like, or alternatively a venturi, static
mixer, ejector, eductor, opposed jet-equipped mixing chamber, or
other device, structure or assembly that effects mixing of the
active fluid and the diluent fluid to produce the diluted active
fluid mixture. As a specific example, one mixing device that can
advantageously be employed in the practice of the invention is a
ConPro Tec ST250-36 static mixer, commercially available from
ConPro Tec, Inc. (Salem, N.H., USA). The mixer in another
embodiment is constituted by a mixing chamber housing a mixing
device, arranged to mix active gas with diluent gas.
[0071] The monitor arranged to sense concentration of active fluid
in the diluted active fluid mixture, and responsively control the
dispensing rate of the active fluid, to achieve a predetermined
concentration of active fluid in the diluted active fluid mixture,
can be of any suitable type, including spectrometric,
spectroscopic, electrochemical, acoustic, thermal, photometric,
chromatographic, colorimetric, surface acoustic wave (SAW),
photonic and flame ionizer types. Preferred monitor types include
TPIR, Fourier Transform-Infrared (FT-IR) and IR photometric
monitors. The monitor can be arranged in any suitable manner, e.g.,
disposed in-line in the diluted active fluid mixture discharge
line, or disposed to sample fluid via a side-stream sampling
arrangement, or in any other suitable fashion.
[0072] The monitor can include one or multiple monitoring devices
or components, as desired in a given application of the invention.
In instances where multiple monitor devices are employed, to
provide monitoring via different sensing modalities, the signals
generated by each of the constituent monitoring devices or
components that are indicative of the concentration of the active
fluid in the diluted active fluid mixture can be processed to
provide an average or corrected output signal correlative to the
concentration of the active fluid in the diluted active fluid
mixture. For such purpose, the monitor can be operatively coupled
with a controller, so that the controller responds to the signal(s)
from the monitor(s) in the system, and responsively adjusts the
system to maintain a predetermined concentration of the active gas
in the multicomponent gas mixture formed by the active gas and the
carrier gas.
[0073] Such signal processing can be carried out by a programmable
general purpose computer that is programmed to process the
respective output signals of the respective monitoring devices or
components, according to a suitable algorithm or computational
procedure, to provide a net output signal correlative of the
concentration of the active fluid in the diluted active fluid
mixture. Alternatively, the signal processing can be carried out by
a comparator or bridge circuit, microprocessor, central processing
unit (CPU) or other processor, to provide appropriate output for
modulating the fluid flow metering device to achieve the desired
active fluid concentration in the diluted active fluid mixture.
[0074] The active fluid in the dilute fluid supply system of the
invention can be of any suitable type, depending on the specific
diluted active fluid mixture-using process for which the diluted
active fluid mixture is to be provided. The fluid can for example
be a gas that is a source material for forming a dopant or trace
reagent species, for manufacturing of semiconductor or other
microelectronic products. The fluid alternatively could be diluted
for use as a calibration standard, as a sterilant for use below
hazardous concentration levels, as a reactant for
nano-concentration chemical reactions, or used for preparation of
low concentration mutagenic agent samples, for research and testing
purposes, etc. The active fluid, although typically constituting a
single component fluid, can in some embodiments of the invention be
provided as a premixed gas mixture, which then is blended with a
diluent gas. The diluent gas in turn may be a single component or a
multicomponent gas.
[0075] The diluted active fluid mixture-using process can be
correspondingly varied, and can variously include industrial
processes, medical diagnostics, research investigations,
agricultural assays, treatment of the body with dilute radiological
therapeutic agents, etc. In a preferred end use, the diluted active
fluid mixture is dispensed for use in ion implantation to form
semiconductor devices or integrated circuitry structures or
substrates in microelectronic device manufacture.
[0076] The diluent fluid can be of any suitable type, and can
variously include single component diluent compositions, as well as
multi-component diluent formulations. Illustrative potentially
suitable diluent fluids in specific applications of the invention
include, without limitation, nitrogen, argon, helium, air, krypton,
xenon, xenon halides, hydrogen, oxygen, ammonia, and gaseous
organometallic compounds.
[0077] Referring now to the drawings, FIG. 1 is a schematic
representation of a gas delivery system 10 arranged to supply a
dilute gas mixture to an ion implantation semiconductor
manufacturing tool 20.
[0078] The dilute gas supply system 10 includes a neat active gas
source 12, which may for example compromise a fluid storage and
dispensing vessel such as a conventional high-pressure gas cylinder
or alternatively a sub-atmospheric pressure gas dispensing system,
e.g., of the type disclosed in U.S. Pat. No. 5,518,528 to Glenn M.
Tom, et al. or the type disclosed in U.S. Pat. No. 6,089,027 to
Luping Wang, et al.
[0079] The neat active gas source 12 thus may comprise a vessel
equipped with a valve head, or alternatively coupled with an
external regulator, restricted orifice flow control element(s), and
other conventional flow circuitry elements. The valve head can
contain a conventional flow control valve (head valve) controllable
by a hand wheel actuator, or alternatively by an automatic valve
controller, e.g., a pneumatic actuator, or electrical solenoid
valve actuator, etc.
[0080] The neat active gas source 12 is coupled in closed gas flow
communication with discharge line 22 having valve 24 and variable
restricted flow orifice (RFO) 24 disposed therein. The discharge
line 26 downstream of the variable RFO 24 is coupled to mini-pump
28. The mini-pump is operable to pump neat active gas from
discharge line 26 into branch line 30, for flow therefrom into line
36 and passage to static mixer 38, along with the added diluent gas
in line 36. As a specific example, one such mini-pump that may be
usefully employed in the practice of the invention is a MB-41
bellows pump, commercially available from Senior Operations, Inc.
(Sharon, Mass., USA). Illustrative of variable RFO devices that may
be useful in the practice of the invention is the Model 1 VSO
valve, commercially available from Pneutronics Division of
Parker-Hannifin (Hollis, N.H., USA).
[0081] A dilute gas source 14 is provided in the system, and
arranged to discharge diluting gas in line 32 to electronic
pressure controller (EPC) 34 for flow therethrough and discharge
from the EPC in line 36 for flow to the static mixer 38.
Alternatively, a rotary mixer, impeller mixer, eductor, or other
mixer could be employed.
[0082] The static mixer 38 functions to blend the active gas and
the diluting gas, to form a diluted active gas mixture that is
discharged from the static mixer in line 40 and passed to the TPIR
unit 42 for analysis to determine concentration of the active
component in the diluted active gas mixture.
[0083] The TPIR in-line gas analyzer 42 is constructed and arranged
to generate an output control signal indicative of the
concentration of the active gas in the diluted gas stream flowing
through the analyzer from line 40 and dispensed from the analyzer
42 in line 44 for flow to the mass flow controller 18. The
controlled flowrate stream of diluted active gas mixture is
discharged from the mass flow controller 18 into line 46 and flowed
therein to downstream gas-using process unit 20, e.g., an ion
implant facility or other semiconductor process tool or
microelectronic device manufacturing installation.
[0084] An electronic signal indicative of the dilute gas
concentration in the gas mixture is generated by the TPIR in-line
analyzer 42 and is transmitted in signal transmission line 48 to
controller 50. The controller 50 responds by generating a control
signal that is transmitted in signal transmission line 52 to the
variable RFO 24 to adjust the setting of the RFO device and thereby
modulate the flow rate of the neat active gas in discharge line 26
that is flowed to the mini-pump 28 for pumping through lines 30 and
36 to the static mixer 38, so that a predetermined concentration of
active gas component is maintained in the gas mixture flowed to the
TPIR analyzer 42.
[0085] Concurrently, the EPC unit 34 functions to maintain a
constant set point pressure in the flow path including gas flow
lines 36, 40 and 44, so that the pressure of the diluted gas
mixture entering the downstream mass flow controller 18 is
maintained constant at a desired pressure level. Although the
pressure controller is typically employed as a separate and
independent component of the blended gas delivery system, in
relation to the fluid flow metering device, in some embodiments of
the invention the pressure controller can serve as a fluid flow
metering device, obviating the need for a separate metering device
component.
[0086] As shown in FIG. 1, the components of the gas delivery
system 10 including variable RFO 24, mini-pump 28, EPC 34, static
mixer 38, TPIR analyzer 42, and controller 50, along with
associated gas flow lines and signal transmission lines, may be
provided in a unitary enclosure 16, to provide a gas blender box as
a modular unitary apparatus, with lines 22, 32 and 44 protruding
from the gas blender box, or otherwise terminating at the box
surface in ports, connectors or other coupling structure, to
facilitate connection of such lines to active gas supply 12,
diluent gas supply 14 and external flow controller 18,
respectively.
[0087] In operation, neat (100% concentration) active gas is
dispensed from neat gas source 12 into discharge line 22 containing
variable RFO 24, which operates to control the delivery rate of the
neat gas. Line 22 contains isolation valve 17, which is open during
the dispensing of gas from the neat active gas source 12, while
isolation valve 21 in the branch line 19 is closed. The resulting
modulated flow rate neat gas from active gas source 12 in discharge
line 22 is pumped by mini-pump 28 through line 30 to line 36 for
introduction to the static mixer 38 for mixing therein with the
diluting gas stream flowed from diluting gas source 14 through line
32 and EPC 34 to line 36. The resulting mixed dilute gas stream
(constituted by the active gas and diluting gas) is flowed in line
40 to the TPIR in-line gas analyzer 42, where concentration of
active gas in the gas mixture is determined and used to
responsively generate the control signal transmitted in signal
transmission line 48 to the controller 50. The controller
responsively generates a control signal transmitted in line 52 to
modulate the variable RFO, i.e., to increase or decrease the active
gas delivery rate to achieve the desired diluted active gas
concentration in the diluted active gas mixture in line 44 flowed
to the downstream process unit 20.
[0088] Although illustratively described as a TPIR unit, the
in-line gas monitor/analyzer 42 alternatively can operate by any
suitable mode of operation, including for example, photometry,
spectroscopy, electrochemistry, acoustic monitoring, thermal
monitoring, etc., or a combination of two or more of such modes of
operation, to determine concentration of active gas in the gas
mixture as diluted for flow to the downstream gas-using process. In
one alternative embodiment of the invention, the gas
monitor/analyzer is an infrared photometric monitor of the type
disclosed in U.S. Pat. No. 6,909,973.
[0089] Additionally, while the embodiment shown in FIG. 1 is
arranged with the fluid flow metering device dispensing the active
fluid, the monitor sensing concentration of active fluid, and the
pressure controller controlling diluent fluid flow, the delivery
system shown in FIG. 1 may alternatively be configured so that the
fluid flow metering device is arranged to dispense the diluent
fluid, the monitor is arranged to sense concentration of the
diluent fluid in the diluted active fluid mixture, and the pressure
controller is arranged to control active fluid flow to maintain the
predetermined pressure of the diluted active fluid mixture
dispensed from the system. As a still further alternative, multiple
fluid flow metering devices, monitors and pressure controllers may
be employed for each of the active and diluent streams, and/or
multiple active and/or diluent fluids can be blended in the blender
delivery system, as may be necessary or desirable in a given
application of the invention.
[0090] The active fluid as mentioned can be of any suitable type,
including, for example, in the case of semiconductor process or
other microelectronic process usage, gases such as hydrides (e.g.,
arsine, phosphine, silane, germane, etc.), acid gases (e.g.,
SiHCl.sub.3, SiF.sub.4, SiH.sub.2Cl.sub.2), boranes, etc. Diluting
gases for such semiconductor or microelectronic device
manufacturing applications can include, for example, homonuclear
diatomic species (e.g., H.sub.2, N.sub.2, O.sub.2) or atomic gases
(e.g., argon, helium, and the like). The active fluid can be a
single component fluid, or alternatively, a multicomponent fluid,
as may be appropriate in a given implementation of the invention.
Illustrative gases that may be present in or constitute the active
fluid in specific applications of the invention include, without
limitation, arsine, phosphine, hydrogen, nitrogen trifluoride,
ammonia, nitrous oxide, tungsten hexafluoride, hydrogen chloride,
chlorine, hydrogen bromide, diborane, methane, methane, ethylene,
chloroform, propane, butane, sulfur hexafluoride, nitrogen,
fluorine, ammonium fluoride, ammonium phosphate, ammonium
hydroxide, boron trifluoride, boron trichloride, dichlorosilane,
germane, tetrafluoromethane, trifluoromethane, difluoromethane,
methyl fluoride, hexafluoroethane, pentafluoromethane,
perfluoropropane, octafluorocyclobutane, nitric oxide, silane,
silicon tetrachloride, silicon tetrafluoride, trichlorosilane,
hydrogen selenide, and organometallic reagent gases.
[0091] It will be recognized that while the invention is
illustratively shown with reference to delivery of dilute gas
species as the active fluid, the invention is also amenable to
delivery of blends of materials in the liquid phase including an
active liquid of a desired concentration.
[0092] It will also be recognized that the dilute fluid supply
system of the invention can be operated and arranged to supply a
plurality of active species; e.g., a blend of complex dopants.
[0093] In another embodiment, the active fluid and/or the diluent
fluid may include a supercritical fluid.
[0094] The safety advantages of utilizing the system of the present
invention are enhanced when the active fluid source is a
sub-atmospheric gas source such as those of the aforementioned Tom,
et al and Wang, et al patents.
[0095] Thus, the system of the present invention, by virtue of its
use of a real-time fluid monitor, provides a continuous measure of
the fluid mixture to ensure a constant diluted active fluid
concentration in the delivered dilute fluid mixture, and at the
same time provides the delivered dilute fluid mixture at a set
point pressure (determined by the EPC or other pressure controller
unit) that accommodates downstream flow control by the end user,
without loss of accuracy of the in-line analyzer or deviation from
the desired concentration level of the active fluid component in
the diluted fluid mixture. If active fluid concentration deviates
from a set point value, a control signal is sent from the fluid
monitor to the active fluid metering device, e.g., the variable
RFO, to increase or decrease the active fluid delivery rate to
maintain the desired concentration value.
[0096] When embodied in a gas blender box as described hereinabove,
the system of the invention provides a conveniently transported and
installed point-of-use gas delivery unit, which can be readily
connected to source gas vessels or other gas supply means and to
the downstream flow controller and gas-utilizing process facility,
to provide the desired amount of diluted gas mixture containing a
precisely controlled concentration of active component.
[0097] By utilizing an electronic pressure controller or other
pressure controller instead of the mass flow controller employed in
prior fluid delivery systems to control the flow of diluent gas, a
constant pressure can be maintained in the gas blender, regardless
of what overall flow rate is selected by the end user for delivery
to the downstream gas-utilizing installation. As an illustrative
example, the MKS 640 Absolute Pressure Controller, commercially
available from MKS, Inc. (Wilmington, Mass., USA), is an electronic
pressure controller that can be usefully employed for such purpose.
Maintaining the gas blender at a constant pressure allows the
analyzer to determine concentration of the diluted active gas
component in an accurate manner at all times.
[0098] Additionally, once the end user turns off the mass flow
controller or other downstream flow control that controls the flow
of the fluid mixture from the fluid blender into the downstream
fluid-utilizing unit, the pressure controller in the fluid blender
system will terminate the flow of the diluent fluid, since the
pressure inside the fluid blender box will reach the pressure set
point of the pressure controller. At such point, the flow of the
active fluid will also turn off, since the active fluid is being
controlled by the variable RFO (or other flow controller), which is
operatively coupled with the controller that in turn is
interconnected with the in-line analyzer. Once the flow of fluid
mixture from the blender is stopped, the in-line analyzer will
sense the concentration of the active fluid in the fluid mixture,
which will rise slightly above the controller set point, and cause
the variable RFO (or other flow controller) to close by action of
the controller, thereby terminating the flow of active fluid into
the blender as well.
[0099] Subsequently, when the end user initiates flow of the fluid
mixture from the fluid blender to the downstream gas-utilizing
installation, the EPC (or other pressure controller) will allow the
flow of diluent fluid into the fluid blender again, so that the
overall pressure in the blender is maintained at the EPC (or other
pressure controller) set point, and the variable RFO (or other flow
controller) will open up again to allow the active fluid to enter
the blender as well, so that the active fluid concentration set
point of the controller is thereafter maintained.
[0100] The blender delivery system of the invention also can be
implemented with an end point detection capability and multiple
active fluid packages arranged for sequential use, so that approach
to exhaustion of a package is detected and the exhausting package
is switched out while a fresh package of active fluid is switched
in, to maintain continuity of dispensing operation. The end point
detection capability can additionally be employed if the diluent
fluid source is of packaged form, with corresponding switching of
diluent fluid packages, from an exhausted or near-exhausted package
to a fresh package of the fluid.
[0101] Thus, the gas delivery system 10 shown in FIG. 1 may be
arranged as illustrated with two active gas sources 12 and 15,
arranged for operation so that upon exhaustion of the active gas
source 12, such source can be isolated and a fresh source brought
on-stream into active dispensing operation. For this purpose, the
gas delivery system 10 features two active gas sources 12 and 15,
with 12 as previously described being joined by discharge line 22
to the variable restrictive flow orifice 24. An isolation valve 17
is disposed in line 22, so that source 12 can be taken off-stream
when it is exhausted.
[0102] The source 15 contains active gas and is joined by branch
line 19, containing isolation valve 21 therein, to the discharge
line 22. When source 12 is exhausted, flow control valve 17, which
is open during normal dispensing operation from such source, then
is closed, and concurrently flow control valve 21, which
theretofore had been closed, is opened, to enable flow of active
gas from the source 15 through discharge branch line 19 to the
discharge line 22.
[0103] In this manner, source 12 may be switched out to ensure
continuity of flow of active gas, by switch-in of source 15 upon
depletion or approach to depletion of source 12.
[0104] The gas delivery system 10 uses the variable RFO 24 as a
flow control device. The variable RFO is connected to controller 50
and the controller 50 is additionally coupled to the TPIR analyzer
42. The TPIR analyzer measures the gas concentration downstream and
responsively sends a concentration-sensing signal to controller 50
through signal transmission line 48. Based on the controller
concentration set point, the orifice of the variable RFO 24 will
either open or close until the concentration set point in the
controller 50 matches the TPIR concentration reading.
[0105] As active gas flows from the on-stream source 12, the
pressure inside such source decreases. As the source pressure
decreases, the orifice of the variable RFO 24 will open further so
that the set flow rate of active gas can be maintained. The
variable RFO in one embodiment opens and closes based on the amount
of voltage being supplied to it, as a voltage-responsive flow
control device. The higher the voltage that is supplied to the
variable RFO, the more open is the orifice of such device.
Accordingly, by monitoring the voltage being supplied to the
orifice, the endpoint of the active gas source 12 can be
determined, since as the soiirce 12 is progressively emptied, the
pressure of the active gas dispensed from such source drops as
well. In order to maintain gas concentration at the controller set
point as measured by the TPIR analyzer 42, the orifice of the
variable RFO 24 will continue to open further and further, until
there is no more pressure drop across the orifice. Since the
variable RFO is operated by a voltage source, when maximum voltage
is being supplied to the variable RFO, the source 12 is nearly
empty, signaling the endpoint of such source, and the corresponding
need to isolate such source 12 and switch-in the fresh source
15.
[0106] The controller 50 therefore is programmatically arranged to
monitor voltage being applied to the variable RFO and when such
voltage is at a predetermined value, the controller operates to
transmit a control signal to isolation valve 17 in signal
transmission line 23, to close such valve and thereby isolate the
source 12 so that it can be uncoupled from the flow circuitry and
removed from the gas delivery system. Concurrently, the controller
50 transmits a signal in signal transmission line 25 to isolation
valve 21 in line 19, opening such valve so that fresh active gas
then is supplied to the downstream flow circuitry from source
15.
[0107] While the invention has been has been described herein in
reference to specific aspects, features and illustrative
embodiments of the invention, it will be appreciated that the
utility of the invention is not thus limited, but rather extends to
and encompasses numerous other variations, modifications and
alternative embodiments, as will suggest themselves to those of
ordinary skill in the field of the present invention, based on the
disclosure herein. Correspondingly, the invention as hereinafter
claimed is intended to be broadly construed and interpreted, as
including all such variations, modifications and alternative
embodiments, within its spirit and scope.
* * * * *