United States Patent [191
`Geatz
`
`[54] APPARATUS AND ‘METHOD FOR THE
`TRANSFER AND DELIVERY OF HIGH
`PURITY CHEMICALS
`
`[75] Inventor: Tobin Geatz, Durham, NC.
`
`[73] Assignee: Applied Chemical Solutions,
`Hollister, Calif.
`
`[21] Appl. No.: 583,826
`
`[22] Filed:
`
`Sep. 17,1990
`
`[51] 1111. C15 ............................................. .. B67D 5/08
`[52] U.S.Cl.
`222/1; 222/59;
`222/61; 222/71; 222/135; 222/152; 222/189;
`222/318; 222/399; 137/205; 137/208; 137/209
`[58] Field of Search ............. .. 137/205, 208, 209, 545;
`222/1, 43, 135, 152, 309, 318, 399, 59, 61, 71
`
`[5 6]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`1,460,389 7/1923 Mauclére .......................... .. 222/399
`2,362,724 11/1944 Shea ........... ..
`3.370.755 2/1968 Querner ..... ..
`3,746,570 7/1973 Mclntosh ....... ..
`4,204,612 5/1980 Schraderetal. ............... 5...... 222/59
`
`FOREIGN PATENT DOCUMENTS
`
`0354665 2/1990 European Pat. orr. .......... .. 222/318
`8203023 9/1982 World 1111. Prop. 0. ........ .. 222/318
`
`OTHER PUBLICATIONS
`Advertisement: ChemFill—Chemical Delivery Sys
`
`1llllllllllllllllllllllllllIQIHIIIIlllllllllllllllIllllllllllllllllllllll
`
`SOO5148945A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,148,945
`Sep. 22, 1992
`
`tem-—Brochure of PS1 International, Chaska, Minn,
`Feb. 1988.
`Advertisement: “System Overview and Installation
`Planning” and Overview of Computerized Chemical
`Distribution Systems-Brochure of Systems Chemistry
`Incorporated, Milpitas, Calif., May 1989.
`Advertising Brochure: Unique Solutions to the Han
`dling and Dispensing of Chemicals With a Commitment
`to Quality and Support—lntegrated Designs, Inc., Dal
`las, Tex.
`Primary Examiner—Donald T. Hajec
`Assistant Examiner—l(enneth Bomberg
`Attorney, Agent, or Firm-Ferrill, Logan, Johns &
`Blasko
`ABSTRACT
`[57]
`The present invention provides improved method and
`apparatus for the transfer and delivery of very high
`purity chemicals for use in semiconductor production
`and similar processes. By employing multiple alternat
`ing pressure vessels, chemicals are drawn from virtually
`any bulk source and delivered to one or more end-users.
`The use of a vacuum system to draw chemicals through
`sealed conduits eliminates the need for pumps which are
`a source of both maintenance problems and contamina
`tion in the system. Multiple vessels provide for a variety
`of flow options, which include continuous chemical
`delivery to the end-users, recirculation and regular
`?ltration during periods of low use, and built-in redun
`dancy to avoid system shut down if there is a compo
`nent failure.
`
`37 Claims, 2 Drawing Sheets
`
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`5,148,945
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`US. Patent
`
`Sep. 22, 1992
`
`Sheet 2 0f 2
`
`5,148,945
`
`I“ PC
`
`CUSTOMER COMPUTER
`HARDWARE
`
`DATA ACOUISTTIOM
`AMO AMALYSIS
`SOFTIARE
`
`ASC MASTER
`CONTROL SOFTWARE
`
`INTERFACE SOFT IARE
`
`lie
`-
`PROGRAMMABLE
`CONTROLLER
`f_———"__l
`VALVEI
`VALVE'X'
`VALVE 2
`SEMSORI SEMSOR"X"
`SENSOR 2
`DISTRIBUTION
`SYSTEM I
`
`IIETIIIIIIII
`CONTROL SOFTWARE \
`PROIMTAMMABLE
`PROGRAMMABLE
`CONTROLLER
`CONTROLLER
`F—_I
`I___"__I
`VALVEI
`VALVE'X'
`VALVEI
`VALVE'x'
`VALVE 2
`VALVE 2
`SEMSORI i SEMSOR'X'
`SEMSORI ISEMSOR'X'
`SENSOR 2
`sEIIsoR 2
`DISTRIBUTION
`DISTRIBUTION
`SYSTEM 2
`SYSTEM "x"
`
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`PROGRAMMABLE
`CONTROLLER
`'__
`'
`VALVEI VALVE'X'
`VALVE2
`l'——‘l
`sEIIs0III
`SEN$0R"X"
`sEIIs0R2
`VACUUM PUMPS
`
`I
`l
`PUMPI PUMPZ
`
`3
`
`

`
`1
`
`5,148,945
`
`APPARATUS AND METHOD FOR THE
`TRANSFER AND DELIVERY OF HIGH PURITY
`CHEMICALS
`
`2
`vessel from which inert gas pressure is used to motivate
`chemical to the use areas.
`Although the pump/pressure system is better con
`trolled and is more conducive to use of ?lters to assure
`chemical purity, it still has serious drawbacks in a sub
`micron chemical environment. Again, lift provided by a
`double diaphragm pump is restricted. Further, such
`pumps are prone to degradation-with the by~products
`entering the chemical stream. Finally, the use of a single
`pressure vessel for delivery means that delivery is not
`continuous, but is rather constrained to “batch” sizes
`based on the size of the pressure vessel. If demand ex
`ceeds the volume of the pressure vessel, further deliv
`ery must be “queued” while the pump re?lls the pres
`sure vessel. Alternatively, pressure from the pump that
`is equal to or greater than the pressure of the delivery
`vessel must be applied to the delivery vessel to supple
`ment or re?ll it during demand; this further compounds
`the ?ltration and maintenance problems.
`Accordingly, it is a primary object of the present
`invention to provide a chemical transfer and delivery
`apparatus and method which effectively transfers high
`purity process chemicals from any bulk source and
`delivers them accurately and without contamination to
`end-use stations.
`It is an additional object of the present invention to
`provide such a transfer and delivery system which pro
`vides even ?ow at a consistent velocity so to permit
`accurate ?ltration and to minimize mechanical shock in
`the system.
`_
`It is a further object of the present invention to pro
`vide such a transfer and delivery system which does not
`employ pumps or other transfer apparatus which are
`subject to degradation or maintenance problems and
`which employs a minimum of any other moving parts
`which may be subject to degradation.
`It is yet another object of the present invention to
`provide such a transfer and delivery system which has
`'multiple flow paths so to provide virtually unlimited
`delivery capacity and built-in redundancy to avoid
`complete system shut down in instances of failure of a
`component of the system.
`
`0
`
`15
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention.
`The present invention relates to the transfer, storage
`and delivery of process chemicals. More particularly,
`the present invention provides improved apparatus and
`method for the transfer, storage and delivery of ultra
`high purity chemicals for use in a variety of industries,
`such as in the manufacture of semiconductor wafers and
`similar products.
`2. Description of the Prior Art.
`In many applications in industry today it is extremely
`important to maintain process chemicals free of virtu
`ally all contaminants. For instance, in the semiconduc
`tor industry the purity of chemicals, such as sulfuric
`acid, hydrogen peroxide, and ammonium hydroxide,
`used in semi-conductor wafer production must be pure
`on level of approximately 25 (or fewer) particles per
`milliliter with a particle size of less than a fraction of a
`micron. As a result of these purity standards, many
`25
`conventional methods of chemical transfer and deliv
`ery, such as paddled pumps and similar devices, have
`proven completely unsatisfactory.
`Of further concern in these industries is that many of
`the chemicals employed are toxic and must be carefully
`handled. In order to assure adequate purity and worker
`safety, it is extremely important that such chemicals be
`transferred, stored, and dispensed in a closed system,
`with minimal contact with the environment or workers.
`Generally today one of two methods are employed to
`effectuate high-purity chemical transfer. The ?rst
`method is a “pumped delivery.” In this method a posi
`tive displacement pump, usually an air powered double
`diaphragm type, is employed to provide both lift at a
`suction inlet from the bulk source of the chemicals and
`simultaneous pressure at the output to the enduser. In
`this system, chemical is lifted from a chemical drum,
`driven through a pump, and pushed out to the point of
`use. Although this method is widely employed, it is far
`from satisfactory.
`The de?ciencies of the pumped delivery system are
`manifold. This system is capable of producing only
`minimal lift from the chemical bulk source--usually on
`the order of only a few pounds per square inch. More
`over, this system is replete with contamination prob
`lems: the rapidly expanding and contracting of the
`pump diaphragm material (e.g. Te?on ®) causes me
`chanical degradation, with the degradation by-products
`(many of which being too small to ?lter with state-of
`the-art ?ltration equipment) entering the chemical pro
`cess stream; further, the rapid action of the pump (usu
`ally greater than 60 cycle per minute) creates massive
`impulse in the system with a resulting pulsed ?ow
`which forces particles through ?lters—thus rendering
`60
`the ?lters ineffective. Finally, the mechanical shock
`inherent in this system creates constant maintenance
`problems.
`The other system in general use today addresses only
`some of these problems. In the “pump/pressure deliv
`cry,” a positive displacement pump is again employed
`to provide lift from the bulk source of chemicals. How
`ever, the chemicals are delivered to an intermediate
`
`65
`
`SUMMARY OF THE INVENTION
`The present invention provides improved apparatus
`and method for the transfer and delivery of high purity
`chemicals from any bulk source to multiple end~use
`stations.
`The invention comprises using a vacuum system and
`a pressure system to alternately decompress and pres
`surize a chemical storage vessel. By creating a vacuum
`in the vessel, chemical can be drawn from the bulk
`source to the vessel; by creating a pressure in the vessel,
`chemical may then be delivered to the end-use station
`or to one or more intermediate vessels capable of being
`pressurized. The use of multiple vessels allow simulta
`neous delivery of chemical to end-users and refilling of
`the vessels; this provides essentially unlimited continu
`ous chemical delivery.
`By employing multiple alternating pressure vessels
`and multiple ?ow paths, the present invention readily
`lends itself to many options. These include assuring
`continuous ?ow to endusers, providing recirculation
`and re-?ltration during periods of low use, and provid
`ing redundancy to insure continued delivery of chemi
`cals even when there is a failure of one or more compo
`nents in the system. Microprocessor control of the sys
`tem is readily implemented to provide accurate and
`
`4
`
`

`
`5,148,945
`3
`instantaneous monitoring and control over all facets of
`chemical transfer and delivery.
`The present invention completely eliminates the need
`for in-line pumps which are prone to degradation, con
`tamination, and maintenance problems. Moreover, the
`present invention provides even, controlled ?ow in the
`system which greatly reduces maintenance problems
`and is extremely conducive to accurate ?ltration and
`?uid delivery.
`A completely closed transfer and delivery system is
`provided with the present invention which vastly re
`duces the need to handle any chemicals from initial
`delivery in a bulk source to dispense of the chemicals at
`the end-use station. This avoids both health problems
`for workers and further potential contamination prob
`lems.
`
`DESCRIPTION OF THE DRAWINGS
`The operation of the present invention should be
`come apparent from the following description when
`20
`considered in conjunction with the accompanying
`drawings, in which:
`FIG. 1 is a schematic representation of the preferred
`embodiment of the apparatus of the present invention;
`and
`FIG. 2 is a schematic representation of one embodi
`ment of the control apparatus for the present invention.
`
`25
`
`30
`
`35
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`The present invention provides improved apparatus
`and method for accurately and effectively transferring
`any form of high purity chemical from a bulk source to
`an end-user station.
`As is shown in FIG. 1, chemical is delivered to an
`industrial site in a bulk source container 10 of a volume
`from 5 to 800 or more liters. The bulk source 10 may
`take the form of a drum or other sealed container with
`a top, side, or bottom opening. Generally the bulk
`source 10 has one or more openings in its top, making
`suction removal of chemical from the bulk source in an
`upright position the most convenient method of trans
`fer. A source conduit 12 or 14 is inserted into and at
`tached to the bulk source 10 in any known manner to
`provide for the withdrawal of chemical. Naturally, if a
`top-opening source 10 is employed, the source conduit
`12, 14 should be long enough or include adequate exten
`sions to pass to the bottom of the bulk source 10 to
`assure the complete removal of chemical from the
`source. Multiple source conduits 12, 14 are preferred to
`permit alternating between chemical bulk sources 10 to
`assure continuous transfer. Each of the source conduits
`12, 14 are provided with a ?uid handling valve 16 and
`18, respectively.
`It should be appreciated that as employed throughout
`this description, all ?uid handling valves may be con
`structed from any suitable material appropriate for par
`ticular design speci?cations and the chemicals em
`ployed. As will become apparent, it is important that
`such valves are capable of handling both liquid and gas
`?uids and, preferably, ?uid pressures of 0 to 100 psig.
`Diaphragm-type valves constructed of per?uoroalkoxy
`(PFA) TEFLON @ (i.e. polytetra?uoroethylene) or
`similar material are preferred.
`The source conduits 12, 14 then combine to a main
`source conduit 20 and pass through valves 22 and 24
`and into a lifting vessel 26 via upper port 28 and lower
`port 29. The lifting vessel 26 is also provided with an
`
`4
`opening 30 to attach to a vacuum system 32, and an
`opening 34 to attach to a pressure system 36. The vac
`uum system is controlled by valve 38, and the pressure
`system 36 is controlled by valve 40. For proper opera
`tion, a level sensor 42 should be provided to assure
`accurate monitoring of the ?uid level in the vessel 26. A
`capacitive-type level sensor is preferred. The lifting
`vessel 26 should also be provided with a pressure re
`lease valve 44.
`,
`Again, it should be appreciated that as employed
`throughout this description, all pressure relief valves
`may be constructed from any suitable material and in
`accordance with the appropriate design speci?cations
`for each installation. The preferred pressure relief
`valves are rupture disc type designed to burst when
`pressures exceed user specifications. Generally the
`valves should be designed to open below 100 psig.
`The lifting vessel 26 may be constructed of any suit
`able material and of any required size. Preferably the
`vessel 26 is a multiple layer construction of a stainless
`steel tank (e.g. Type 316L stainless steel, electropol
`ished and passivated), an inner liner of PFA TEFLON
`or similar material, and an outer pressure tank of polyvi
`nyl chloride (PVC). The vessel 26 should have a pres
`sure operational range of O to 100 psig, and a vacuum
`operational range of 700 to 50 torr. The nominal vessel
`size should be approximately 20 liters; however, de
`pending on application, vessel size may reach or exceed
`900-1000 liters.
`The vacuum system 32 comprises ?uid handling
`valve 38, gas evacuation conduit 46, water trap/scrub
`ber 48, and one or more vacuum pumps 50a and 50b.
`Gas is evacuated from the lifting vessel operating a
`pump 50 to create a negative pressure in the evacuation
`conduit 46 and then by opening valve 38.
`The pumps 50 may be of any construction and size
`necessary to create a negative pressure in the lifting
`vessel of 700 to 50 torr. To adequately evacuate a 20
`liter lifting vessel, a vacuum pump with a 5 to 50 CFM
`capacity should be provided. In order to avoid needless
`system shut downs, it is preferred that multiple pumps
`be provided with automatic switching between them in
`the case of pump failure or need for greater gas evacua
`tion capacity. The water trap/scrubber 48 of known
`construction is provided as means to remove from the
`exhaust through conduit 46 any chemical residues
`which become entrapped in the vacuum stream, and to
`maintain conduit 46 free of any and all contaminants
`which may enter the system from the pump 50. A water
`inlet 52 and a water drain 54 should be provided on the
`trap 48 to permit periodic replacement of the scrubber
`water. Naturally, other ?ltration or scrubber means
`may be substituted for trap 48.
`The pressure system 36 comprises ?uid handling
`valve 40, a pressurized gas conduit 56, a pressure sensor
`57, and a pressurized gas source 58. Sufficient gas ca
`pacity should be provided to pressurize and maintain
`the lifting vessel at a pressure of 0 to 100 psig during
`chemical transfer, and preferably at a pressure of 5 to 15
`psig. Although the choice of gas may varying depend
`ing on particular applications, generally any noble or
`inert gas may be employed, such as nitrogen, argon,
`helium, neon, etc. Nitrogen and argon are preferred for
`most applications due to cost and availability advan
`tages. Control of the application of pressure to the lift
`ing vessel 26 is controlled by valve 40 in conjunction
`with pressure sensor 57.
`
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`5,148,945
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`Chemical exiting the lifting vessel 26 through lower
`port 29 passes through valve 24 and a portion of source
`conduit 20 to transfer conduit 60. Transfer conduit 60
`comprises valve 62, ?lter unit 64, valve 66, and junction
`68. At junction 68 the transfer conduit separates into
`two separate transfer conduits 70a and 70b. Flow
`through transfer conduit 70a passes through valve 720
`and into delivery vessel 740 via upper port 76a and
`lower port 780. Similarly, flow through transfer conduit
`70b passes through valve 72b and into delivery vessel
`7412 via upper port 76b and lower port 7812.
`It should be appreciated that in the preferred applica‘
`tion of the present invention described herein, both the
`delivery vessels 74a and 74b are identical in structure
`and operation. Further, in the embodiment shown, the
`delivery vessels 74 are also identical to the lifting vessel
`26 in structure and operation. Accordingly, each deliv
`ery vessel 74 includes: an opening 80 to attach to vac
`uum system 32 controlled by valve 82; an opening 84 to
`attach to pressure system 36 controlled by valve 86 and
`pressure sensor 88; a level sensor 90; and a pressure
`release valve 92.
`Although the delivery vessels 74a, 74b may be pro
`vided with their own vacuum system and pressurized
`gas system, it is preferred that appropriate conduits be
`provided to utilize one vacuum system and one pressur
`ized gas system for the entire transfer and delivery
`apparatus.
`Chemical exiting either delivery vessels 74a, 74b
`through lower ports 78a, 78b passes through valve 94a,
`94b, into delivery conduit 96a and 96b, and to junction
`98. At junction 98 the two delivery conduits 96a, 96b
`join to form main delivery conduit 96. Flow through
`delivery conduit 96 passes through valve 100, ?lter unit
`102, valve 104, and may then be split into as many sepa
`rate individual delivery conduits as may be necessary to
`service all end user stations (i.e. points of use) 106. Flow
`to each end user station 106 is controlled by valves 1080
`through 108f
`A number of important options may be readily em
`ployed with the present invention. As is shown in FIG.
`1, a return conduit 110 may be provided from either the
`main delivery conduit 96 or from the delivery conduits
`at the end user stations 106 to provide for the recircula
`tion of chemical back to the bulk source 10 or back
`through the transfer and delivery apparatus during
`times of low use. The purpose of this option is to assure
`the best particle performance, chemical homogeneity,
`and regular ?ltration of all chemicals in the system.
`Flow through return conduit 110 is controlled by
`valve 112. At this stage flow can be directed back to the
`bulk source 10 via return source conduits 1140 or 11412
`through operation of valves 1160 or 116b, respectively.
`Alternatively, flow may continue to recirculate through
`the system. This is accomplished by directing flow
`through conduit 110, valve 118, ?lter unit 120, and
`valve 122 to where return conduit 110 joins source
`conduit 20.
`Although this recirculation process may be accom
`plished manually, it is preferred that the system auto
`matically recirculates chemicals during periods of low'
`or no use. To this end, a flow sensor may be provided in
`conduit 96 to measure low or no flow which then pro
`vides digital feedback to a computer controller, as is
`described below.
`Another option which may be employed is to control
`the ?ow rate to the end user stations 106 using a flow
`control 124 on delivery conduit 96. The flow control
`
`6
`comprises: a flow sensor 126, such as a paddle wheel or
`inductive type, installed in the delivery conduit 96; a
`flow meter 128, preferably digitally controlled which
`may be readily interfaced with a computer controller;
`and a motorized control valve 130, preferably needle
`valve type made from PFA TEFLON, stainless steel, or
`similar material, which will respond to the ?ow meter
`to provide highly accurate flow rates to the end users.
`In the preferred application, a digital flow meter 128 is
`attached to an ultrasonic flow sensor 126 providing a
`digital or analog output (eg 4 to 20 mAmps) to a sys
`tem controller or programmable logic controller
`(PLC).
`It should be appreciated that the interface of the flow
`control 124 with a controller may also provide the
`necessary information on chemical demand necessary to
`direct the automatic recirculation function discussed
`above.
`Another option which may be necessary in many
`applications is the addition of one or more ?lter units
`throughout the system. Such ?lters are shown in FIG. 1
`as elements 64, 102, and 120. The controlled flow possi
`ble with the present invention permits accurate ?ltra
`tion using commercially available ?lter units. As is
`known, for applications such as semiconductor wafer
`production, purity of chemicals must be maintained at a
`level of 50 particles per milliliter at greater than 0.3
`micron or l5 particles per milliliter at greater than 0.5
`microns. Semiconductor ?uids must be as free of parti
`cles as possible. As new materials are made available,
`the empirical lower limits can be expected to change.
`However, a basic novelty of the present invention (i.e.
`low impulse transfer) will remain essential. The intent
`of the present invention is not to limit its use to particu
`lar purity applications, but it should be appreciated that
`regardless of media or ?lter size, pulsing flow will al
`ways be a problem as will intimate contact of fluid with
`a centrifugal or rotary vane pump.
`Acceptable commercially available ?lter units in
`clude those consistent with MILLIPORE 0.05 micron
`TEFLON media available from Millipore Corporation
`of Bedford, Mass. Filter units may be any form as is
`compatible with the particular use of the present inven
`tion. Generally such units are those ?ltering 0.1 to 0.05
`microns absolute (and which also pass a bubble point
`test).
`The size and speci?c ?ltration requirements are heav
`ily application dependant. For most semiconductor
`applications employing 20 liter lifting and delivery ves
`sels, three ?lter units as shown in FIG. 1 with a ?ow
`capacity of 0 to 40 or greater liters per minute and
`providing ?ltration at a level of at 10 particles per milli
`liter at less than 0.2 microns is sufficient.
`Not only do the use of filters assure the removal of
`any contamination generated in the system and help
`maintain the homogeneity of the chemicals, but accu
`rate filtration may also provide chemical to end user
`stations which exceed the purity level of the chemicals
`delivered from the bulk source. It should be appreciated
`that any of the ?ltration steps described herein may be
`comprised of two or more ?lters oriented in parallel.
`This arrangement allows service of one ?lter element
`while others remain on-line and active.
`Other options which may be employed with the pres
`ent invention are additional outlets throughout the sys
`tem to provide for periodic sampling and monitoring.
`Two such outlets are shown on delivery conduit 96 in
`FIG. 1. Outlet 132 may be used to pass chemical to a
`
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`
`8
`Once the lifting vessel is ?lled with chemical, valve
`40 is then opened and inert gas pressure is applied to the
`lifting vessel 26 to provide motive force for transfer to
`either of the two delivery vessels 740 or 746. When the
`desired pressure is reached (e.g. 5 to 15 psig), valves 24,
`62, 66, and 72a are opened and chemical is tranferred to
`delivery vessel 740 through ?lter unit 64. If air has not
`been previously removed from the delivery vessel 740,
`then valve 820 should also be opened at least in part to
`permit standing gas in the delivery vessel 74a to be
`displaced by the incoming chemical.
`The steps employed to ?ll and pressurize the lifting
`vessel 20 26 may then be repeated. Delivery vessel 74b
`may be ?lled by opening valves 24, 62, 66, and 72b (and,
`again if necessary, valve 82b).
`
`15
`
`5,148,945
`7
`particle counter to provide either constant or periodic
`monitoring of the purity of the chemical in the delivery
`conduit 96. Outlet 134 may be used to pass chemical to
`various other analytical apparatus, such as an atomic
`absorption analyzer (AA), gas chromatograph (CG), or
`similar devices.
`As is shown in FIG. 2, the present invention particu'
`larly lends itself to operation using available micro
`processor controls to direct the flow through the sys
`tem. In “Distribution System 1” 136, a programmable
`controller, such as a dedicated microprocessor or lad
`der logic controller, or a dedicated personal computer,
`may be employed to respond to various digital sensors
`provided throughout the system. Such sensors include
`the level sensors 42, 90a, 90b, pressure sensors 57, 88a,
`88b, and flow sensor 126. It should be understood that
`other conventional sensors may be installed throughout
`the system to monitor ?ow through and/or pressure in
`various conduits.
`Employing motorized control valves of known con
`struction, the programmable controller may then in
`stantaneously control the flow of chemical throughout
`the system and adjust for changes in demand or prob
`lems in the system. A user interface also allows instant
`command processing for all necessary maintenance,
`including purging the system of any given chemical.
`As is further shown in FIG. 2, use of known network
`hardware and software permits the present invention to
`be controlled in parallel with one or more other chemi
`cal transfer and delivery systems. One advantage of
`such a networked system is that a single bank of vacuum
`pumps 138 and/or pressurized gas source may be em
`ployed to operate multiple distribution systems.
`The present invention may be employed to transfer
`and deliver virtually any form of chemical from a“ bulk
`source to a user station. For sub-micron purity semicon
`ductor wafer production, such chemicals include sulfu
`ric acid, ammonium hydroxide, hydrogen peroxide,
`hydrochloric acid, hydrofluoric acid, or numerous
`40
`other organic and inorganic chemicals. The choice of
`materials for the system is heavily application depen
`dant. For most uses, conduits, vessels, valves, etc. may
`be constructed from or lined in stainless steel, PFA
`TEFLON, glass, other ?uoropolymers (e.g. ECTFE,
`45
`or PVDF), or polyole?ns (e.g. polypropylene, or poly
`ethylene).
`The precise method of operation of the present inven
`tion will become clear through the following examples:
`
`EXAMPLE 2
`The delivery of chemical from the delivery vessels 74
`to the point of use or end user stations 106 based on
`demand is accomplished in the following manner:
`In a stand-by state, both delivery vessels 74a, 74b are
`pressurized with inert gas to a desired level (e.g. 5 to 15
`psig) by opening of valves 86a and 86b. All other valves
`remain closed. When a demand is sensed, valves 940,
`100, and 104 are opened, followed by the appropriate
`opening of one of valves 1080 through 108f The inert
`gas pressure forces chemical from delivery vessel 740,
`through ?lter 102, and through open valve 108 to the
`end user station 106. In most applications, a flow rate of
`0 to 100 liters per minute to the end-use stations is suf?
`cient. Chemical will continue to the end user station 106
`until either demand is no longer sensed, or delivery
`vessel 74a is approaching empty.
`If delivery vessel 74a is approaching empty, this in
`formation is conveyed by level sensor 90a. If demand is
`still sensed, valve 940 is closed and valve 94b is opened,
`allowing chemical to ?ow uninterrupted from delivery
`vessel 74b to the end user station 106. While chemical is
`delivered from delivery vessel 74b, delivery vessel 740
`may be re?lled in the manner described in Example 1,
`above.
`By alternately switching between delivery vessels in
`this manner, a continuous ?ow of chemical may be
`provided to the point of use so long as required. Once
`demand at the end user stations 106 ceases, the sequence
`described in Example 1 is repeated until both delivery
`vessels 74a, 7412 are ?lled and in the stand-by state.
`
`EXAMPLE 3
`The identical construction of the lifting vessel 26 and
`both delivery vessels 74a, 74b in the preferred embodi
`ment of the present invention described herein is pro
`vided to assure built-in backup in the case of a failure of
`one or more vessels in operation. If one of the vessels
`fails to function, all necessary valving is provided to
`permit either of the remaining vessels to serve as either
`a lifting or delivery vessel. It should also be understood
`that the present invention will also function with only
`one operating vessel, in which case it will serve as both
`a lifting vessel and a delivery vessel. Naturally if opera
`tion is reduced to a single vessel, continuous supply can
`no longer be provided and chemical is then delivered in
`a “batch” manner, with further demand held waiting
`while the vessel re?lls.
`
`EXAMPLE 4
`
`At times of no demand, constant recirculation can be
`provided to provide constant ?ltration and insure that
`
`55
`
`EXAMPLE 1
`To transfer chemical from a commercial tank or bulk
`source 10 into the delivery vessels 74, the following
`procedure is employed:
`The chemical bulk source 10 is attached to source
`conduits 12, 14. A minimal vacuum pressure (e. g. 600 to
`3(1) torr (application dependent» is applied to lifting
`vessel 26 by operating vacuum system 32 and opening
`valve 38 with all other valves closed. When the desired
`pressure is reached, valves 22 and 24 are opened fol
`60
`lowed by valve 16 or 18 (i.e. depending on the nature of
`the bulk source attachment and the particular bulk
`source from which chemical is ?rst desired). In this
`manner chemical is drawn into the lifting vessel 26.
`Once the level sensor 42 indicates that the lifting vessel
`26 is ?lled, valve 16 or 18 is closed followed by the
`closing of valves 22 and 24. Valve 38 is then closed to
`discontinue vacuum in the lifting vessel 26.
`
`65
`
`7
`
`

`
`5,148,945
`
`chemical remains up to speci?cation. This may be ac
`complished in the following manner:
`When no demand is called for and both delivery
`vessels 74a, 7412 are ?lled, the lifting vessel continues
`through the ?ll sequence described in Example 1,
`above. However, instead of transferring chemical to the
`delivery vessels 74a, 741;, the lifting vessel transfers
`chemical back to the bulk source 10 by opening valves
`122, 118, and either 1160 or 11617.
`
`10
`providing a source conduit between the bulk source
`and the lifting vessel, includign a valve to control
`?uid flow through the source conduit;
`providing a vacuum system in communication with
`the lifting vessel and including means to evacuate
`gas selectively from the lifting vessel;
`providing a pressure system, operated independelty
`of said vacuum system, in communication with the
`lifting vessel and including means to pressurize
`selectively the lifting vessel;
`providing a delivery vessel in communication with
`the lifting vessel;
`providing a delivery conduit from the delivery vessel
`to the end-use station, including a valve to control
`fulid ?ow through the delivery conduit;
`providing connecting conduits among the lifting ves
`sel, the delivery vessel, and the end use station,
`includign valving to regulate ?ow through such
`conduits, so as to all