Apparatus and method for pumping high viscosity fluid

A system for dispensing and filtering fluid is disclosed, in which the fluid flow path is substantially vertical from the fluid inlet through fluid dispense. Substantially all wetted surfaces are Teflon.RTM. or some similar non-contaminating fluid, for applications such as cleanroom processes. A valve and a filter chamber are incorporated into a pump head to simplify the flow path and reduce potential contamination points. Preferred methods, and chips or other microelectronic devices fabricated from the apparatus or methods, are also disclosed.

The present invention relates to pumps for precisely dispensing fluids and
 methods related thereto, as well as various products made by those pumps
 and methods.
 BACKGROUND OF THE INVENTION
 This invention relates to a pumping system useful in dispensing fluids,
 especially those that are expensive, viscous, high purity, and/or
 sensitive to molecular shear. The invention also relates to
 microelectronic components such as silicon chips and wafers,
 microelectronic substrates, and circuits fabricated by such pumping
 systems and methods, including the potentially improved quality and yield
 of such products achievable with the invention as compared to prior art
 systems.
 General aspects of the relevant background of the invention are discussed
 in prior U.S. Pat. Nos. 5,167,837; 5,772,899; and 5,516,429. Among other
 things, the invention has numerous applications, but is especially useful
 in the microelectronics industry. The trend in that industry continues to
 be to squeeze greater quantities of circuitry onto smaller substrates.
 Circuit geometries continue to shrink, the use of expensive materials
 continues, and the corresponding need for decontaminated "cleanroom"
 environments and equipment for manufacturing, filtering, and processing
 continues and even increases. Perhaps as importantly, the need for
 improved yield of final product continues, for economic and other reasons.
 The equipment and methods of the aforementioned U.S. Pat. Nos. 5,167,837;
 5,772,899; and 5,516,429 addresses many situations and applications very
 well. The present invention is directed to further improvements in that
 technology, as well as potential applications of such improvements in
 unrelated technologies.
 Among other things, further simplification and upright orientation of the
 flow path for the processed fluids through a pumping and dispensing system
 can reduce the risk of contamination, air entrapment, or similar concerns,
 while providing similar or improved reliability and precise control for
 desired filtration, dispense, and other handling of the process fluids.
 Further manufacturing and design improvements in the instant invention
 allow the entire process fluid flow path to be coated or machined from
 Teflon.RTM. or some similar non-contaminating material, further reducing
 the likelihood of any contamination problems.
 As indicated above, many problems were addressed and solved by the
 aforementioned U.S. Pat. Nos. 5,167,837, 5,516,429, and 5,772,899. Among
 other things, those devices introduced a diaphragm-type fluid dispense
 system which, in certain embodiments, included two separate
 computer-controlled pumps to dispense precise amounts of fluid. However,
 the preferred embodiments in those patents show the process fluid
 traveling in a somewhat meandering path through the pump system. In
 certain applications, that path does not afford optimal venting for any
 contaminating air bubbles that may become entrapped in the fluid or the
 system. For example, some small amount of air bubbles may be unavoidably
 introduced when the source fluid container is periodically changed, even
 if no re-priming is required. Portions of the flow path that are metal or
 otherwise relatively potentially contaminating result in some risk
 (however small) of corresponding undesirable contamination of the fluid.
 As indicated in those prior patents, such bubbles or contaminants could
 potentially compromise the end product to some degree in some small
 percentage of applications. Alternatively, such bubbles or contaminants
 might require some period of "flushing" bubbles from the system upon
 changing the source fluid container, for example, or might otherwise
 compromise the accuracy of the fluid dispense system (again, in a small
 percentage of applications and situations). Although those prior patents
 and inventions function well in that regard and are a dramatic advance
 over the prior art before them, and although those prior patents can be
 readily adapted to deal with the aforementioned potential problems, the
 instant invention provides improvements in that regard.
 Other benefits derive from simplifying the flow path of the fluid. By
 simplifying and reducing the number of components involved in the system,
 assembly and maintenance can be correspondingly simplified. Perhaps more
 importantly, the number of connection points, seals, fittings, and related
 potential leak-spots can be reduced, thereby directly reducing the risk of
 contamination, air-entrainment, or similar problems. Additionally,
 reducing and realigning the fluid flow path can reduce the size of the
 "footprint" for the housing of the system and otherwise make the system
 more compact as compared to prior art systems, thereby correspondingly
 reducing valuable factory space for the users of the pump system.
 OBJECTS AND ADVANTAGES OF THE INVENTION
 It is, therefore, an object of my invention to provide a fluid dispensing
 system that provides the improved performance and benefits discussed
 herein. The system is characterized by substantially vertical fluid flow
 from its inlet to its outlet when the system is in its normally upright
 position, and by providing Teflon.RTM. or similar non-contaminating wetted
 surfaces throughout the flowpath. In its preferred embodiment, the flow
 path is simplified as compared to prior art systems, including fewer
 fittings and connections (in part resulting from integrally forming
 various components into single unitary structures).
 A further object of the invention is the provision of a device for
 processing fluid in a precisely controlled manner, including the
 combination of first pumping means and second pumping means in fluid
 communication with each other, in which the fluid travel path that is
 substantially consistently upward as the fluid flows through the first
 pumping means and the second pumping means. As indicated above, the first
 and second pumping means surfaces that contact the fluid are preferably
 all fabricated from or coated with a relatively non-contaminating
 material, such as Teflon.RTM. or the like. Among other things, this
 facilitates using the system for high-purity fluids, in cleanroom
 environments, etc.
 The device can further include filter means between the first pumping means
 and the second pumping means, in which case the fluid travel path
 preferably remains substantially consistently upward as the fluid flows
 through the first pumping means, the filter means, and the second pumping
 means, and all or substantially all contacting surfaces are
 non-contaminating. In the preferred embodiment, the pump head and the
 valve therein are actually fabricated from Teflon.RTM., and all fittings
 along the flow path are flare fittings formed from Teflon.RTM. or
 otherwise having wetted surfaces that are non-contaminating to the subject
 fluid. For the non-contaminating aspect of the invention, the particular
 material may be any suitable non-contaminating material, including without
 limitation various forms of Teflon.RTM. (TFE & PFA), Kalrez (a
 fluorinated, Teflon.RTM. -like elastomer), or other materials. Among the
 many suitable fittings usable in the invention, commercially available
 Furon Flare Grip.RTM. PFA tube fittings can be readily utilized.
 Another object of the invention is the provision of a system or device of
 the aforementioned character, in which the first pumping means includes an
 upper head portion removable from a lower portion, and means are provided
 for temporarily attaching the upper head portion to a lower portion to
 form a pumping chamber therebetween. Preferably, the upper head portion
 includes integrally formed valve means configured to thereafter direct the
 process fluid in a substantially upward path toward a filter chamber
 integrally formed in the upper head portion. Among other things, the
 integral valve facilitates filtering viscous and other fluids under
 relatively low pressure, and decreases molecular shear on the fluids, in
 part by providing relatively larger and less obstructed flow paths through
 the valve (as compared to prior art systems). The valve also reduces
 differential pressure, or pressure drop, as the fluids move through the
 valve.
 An additional object of the invention is the provision of a system or
 device of the aforementioned character, in which the second pumping means
 includes an upper head portion removable from a lower portion, with means
 for temporarily attaching the upper head portion to the lower portion to
 form a pumping chamber therebetween. Again preferably, the upper head
 portion of the second pumping means includes an integrally formed tee
 fluid flowpath therein, wherein the tee provides a substantially direct
 upward flowpath for the subject fluid from the pumping chamber toward a
 dispense from the upper head portion. The preferred tee includes an input
 portion for receiving the subject fluid after it has been pumped by the
 first pumping means, and the dispense from the second pump's upper head
 portion is positioned higher than the input portion when the device is in
 its normal, upright orientation.
 A further object of the invention is the provision of a system or device of
 the aforementioned character, in which the second pumping means is
 positioned generally above the first pumping means, and the fluid travel
 path from an exit of the first pumping means to an inlet into the second
 pumping means does not include any downwardly directed portions when the
 device is in its normal, upright orientation.
 A still further object of the invention is the provision of a device for
 dispensing fluid, including the combination of a first diaphragm-type pump
 having a pumping head, the head including an integrally formed valve to
 control flow of fluid into the first diaphragm-type pump. The device can
 further include a second diaphragm-type pump positioned generally above
 the first diaphragm-type pump and configured to receive fluid pumped by
 the first diaphragm-type pump, and having a fluid path from the first
 diaphragm-type pump to the second diaphragm-type pump that is generally
 upward.
 Yet another object of the invention is the inclusion of a vent valve above
 or upstream of the filter to permit selective venting of any gas entrained
 in the subject fluid. Preferably, the vent valve can also function as a
 pressure relief or safety valve, to prevent the pressure on the subject
 fluid and the system itself from exceeding a selected level. Also
 preferably, the vent valve is positioned at a high point within the filter
 chamber.
 Other objects of the invention are directed to a method for filtering and
 dispensing fluid, including one or more of the steps of providing a valve
 means integrally formed in an upper head of a first pumping member, the
 valve means configured to receive the subject fluid and direct it in a
 substantially upward path from the first pumping member; actuating the
 first pumping member to draw the subject fluid from a source; and further
 actuating the first pumping member to dispense the subject fluid upwardly
 from the first pumping member. In the preferred embodiment, the valve
 switches the fluid flow drawing and dispensing steps in the preceding
 sentence. As indicated above, the steps can further include providing a
 filter chamber integrally formed in the upper head of the first pumping
 member and providing a substantially direct upward flow path within the
 upper head from the first pumping member through the valve means to the
 filter chamber, whereby further actuation of the first pumping member
 directs the subject fluid upwardly from the first pumping member to the
 filter chamber.
 Additional steps of the methods of the invention include providing a second
 pumping member substantially above the first pumping member and providing
 fluid flow means therebetween, whereby the subject fluid does not flow
 downwardly between the first pumping member and the second pumping member;
 and pumping the subject fluid along the non-downward flowpath.
 Another object of the invention is the provision of apparatus and methods
 that include providing a valve downstream of the second pumping member for
 selectively dispensing the subject fluid or returning the subject fluid to
 the source, in which the downstream valve is a substantially zero
 displacement valve that does not undesirably contaminate or introduce gas
 into the subject fluid. Among other things, the preferred valve reduces or
 eliminates the likelihood that operating the valve will displace fluid
 (such as displacing it from the dispense line), which displacement could
 adversely affect the accuracy of dispense or other aspects or performance
 of the system.
 Although the invention is described herein in connection with dispense of
 high-purity, viscous fluids, the invention may be utilized in many other
 applications. Moreover, although the preferred embodiment discussed herein
 includes two pumping means with filter means interposed therebetween,
 advantageous aspects of the invention may be practiced with no filter
 means, or with only one pumping means with or without filter means.
 As with prior art systems, my invention provides a dispensing system
 permitting the use of computer or other automated digital control for the
 rate and interval of dispense, as well as for the direction of fluid flow
 through the system and fluid pressure during operation of the system.
 Thus, still another object of my invention is the provision of a
 dispensing system that permits great flexibility of operation, making it
 adaptable to numerous applications. The system may be controlled or driven
 by stepper or servomotors, or similar technology, and by various computer
 software, hardware, and wiring or wireless communication systems.
 Other objects of my invention include providing a relatively shorter fluid
 flow path such that contaminants are less likely to be introduced, and a
 relatively more compact pump design that leaves a smaller "footprint" (as
 compared to prior art devices).
 An additional object of the invention is the provision of integrated
 circuits, chips, or other microelectronic devices fabricated from the
 aforementioned apparatus or methods.
 Other objects and advantages of the invention will be apparent from the
 following specification and the accompanying drawings, which are for the
 purpose of illustration only.

DESCRIPTION OF PREFERRED EMBODIMENT
 Referring now to the drawings, and particularly FIGS. 1 and 2, I show a
 preferred embodiment of a pump and dispense system 10 constructed in
 accordance with the teachings of the invention. Preferably, the system
 includes a first pumping means or master pump 20, and a second pumping
 means or slave pump 30, operably connected to pump fluid from an inlet 12
 to an outlet 46. As described herein, filtering means can be included
 between the master and slave pumps 20 and 30, or preferably within the
 master pump 20 (as described herein), to filter the process fluid.
 General concepts regarding the components and operation of the preferred
 system and its pump mechanisms are disclosed in U.S. Pat. Nos. 5,167,837,
 5,516,429, and 5,772,899, which are hereby incorporated herein by
 reference. An overview of a preferred method of operation of the present
 invention is illustrated in FIG. 8. Fluid taken from an initial fluid
 source 60 (FIG. 8) is drawn into the system 10 through the inlet 12, by
 operation of the master pump 20. As part of this process, an integral
 three-way valve 140 in the master pump is positioned to permit the subject
 fluid to be pulled into a diaphragm-style first pump 18 (by moving its
 diaphragm downwardly, as explained in the aforementioned patents). The
 valve 140 is then actuated to permit flow from pump 18 upwardly through
 valve 140 and eventually through a filter 27. One or more vent or check
 valves (such as vent valve 36 and check valve 49) can be included along
 the flowpath at appropriate locations, to vent undesirable entrained gas
 and to prevent undesirable backflow, as discussed further herein. The vent
 valve 36 can either return the fluid to the source 60 (as shown in FIG. 8)
 or to a waste drain (not shown). When exiting the filter other than via
 the vent valve 36, the fluid preferably travels to a second
 diaphragm-style pump 44, which preferably directs it to another three-way
 valve 99 (see FIG. 8; that valve 99 can be any suitable valve, such as the
 zero-displacement, non-contaminating valves described herein, and can be
 positioned at any suitable location, although it typically is remote from
 the second pump 44 so as to be adjacent the actual dispense and improve
 the ability to precisely control final dispense, dripping, suckback or the
 like). That second valve 99 can be selectively actuated to direct the flow
 back to the source 60 or to be dispensed on a substrate or other
 microelectronic chip or device-in-process (not shown).
 Persons of ordinary skill in the art will understand that many of the
 general concepts disclosed in the aforementioned U.S. Pat. Nos. 5,167,837,
 5,516,429, and 5,772,899 apply with equal cogency to this invention. Some
 of the important improvements over those prior art inventions are
 disclosed or described herein.
 By way of example and not by way of limitation, the overall flow path for
 the subject fluid is preferably substantially upward as the fluid moves
 through the system 10 (obviously, however, if the fluid is directed by
 valve 99 back to the source, the fluid then returns "down" to its original
 level). This preferred upward flow path includes preferred positioning of
 the inlet 12 as low as practicable on the first pumping member 20.
 Preferably, the only "down" flow portions of the flow path occur as the
 fluid is drawn into the respective pumping chambers 18 and 44. Persons of
 ordinary skill in the art will understand that this "down" flow
 facilitates priming of the pumps and other beneficial performance and
 packaging of the system 10 (including facilitating practical packaging of
 the preferred hydraulics, diaphragm pumps, and pump heads and filters
 within a relatively small footprint), and that in any case the preferred
 substantially vertical alignment and configuration of the "downstream"
 components and elements adjacent each of those pumping chambers 18 and 44
 minimizes any gas entrainment or related problems that might otherwise
 occur. For example, the preferred embodiment provides relatively vertical
 passages 22, 23 and 45 (see FIGS. 3 and 7) from uppermost respective
 regions of those pumping chambers 18 and 44, to a vent valve 36 (see FIG.
 6) and to the exit of the second pump 46. Thus, in the preferred
 embodiment, any "downward" flow is immediately followed by an upward flow
 (via the diaphragm pump forcing the subject fluid in an upward direction),
 which helps to purge any entrained air and to continue the overall upward
 flow of the subject fluid.
 Similarly by way of example and not by way of limitation, and as more fully
 explained herein, the overall flow path preferably includes fewer fittings
 than prior art systems, and those fittings and the flow path itself are
 preferably fabricated from or coated with Teflon.RTM. or similar
 materials, to further reduce the risk of any contamination of the process
 fluid. Preferably, and as indicated above, flare fittings such as
 commercially available Flare Grip.RTM. PFA tube fittings can be readily
 utilized.
 In FIG. 3, the preferred embodiment is illustrated as including the first
 pumping chamber 18 being formed by assembling an upper head portion 120
 with a lower portion 122, sealing and binding a flexible diaphragm 124
 therebetween. A sealing element 127 is preferably provided to ensure a
 fluid-tight seal. The diaphragm 124 is preferably fabricated or coated
 with Teflon.RTM. or some similar non-contaminating material.
 At least somewhat similarly to the aforementioned U.S. Pat. Nos. 5,167,837,
 5,516,429, and 5,772,899 (especially with reference to FIGS. 2 in each of
 those patents), the diaphragm 124 and lower portion 122 are preferably
 configured to permit precisely-controlled actuation and flexing of the
 diaphragm (and consequent pumping of subject or process fluid) by stepper
 assemblies, servomotors, or similar devices displacing fluid into and from
 the space 125 below the diaphragm 124. In the preferred embodiment, this
 can be accomplished by pumping the relatively incompressible actuating
 fluid through tubing or passageway 126 (connected at its opposite end--not
 shown--to a stepper assembly 180 or its equivalent). Persons of ordinary
 skill in the art will understand, as indicated below, that the passageway
 126 can be any suitable configuration, including (among the many
 alternatives) an "internal" passageway such as passage 226, shown in FIG.
 13. The base elements such as base 161 are preferably fabricated from any
 suitably strong material, although the need for non-contamination is
 somewhat less because the subject fluid is not exposed to the base or any
 passageways therein. Positional feedback flags 184 and 194 and limit
 switches 182 and 192, FIGS. 1 and 2, are preferably provided on the
 pistons or stepper assemblies, to facilitate control and operation of the
 system 10. Among the many alternative embodiments of the invention (such
 as illustrated in FIGS. 9-14) are those using optical limit switches 282
 and 292 that sense flags 284 and 294 that preferably move with the piston
 and extend therefrom.
 Among the many alternative embodiments for the diaphragm actuating means
 are arrangements similar to those illustrated in the aforementioned FIGS.
 2 of the aforementioned U.S. Pat. Nos. 5,167,837, 5,516,429, and
 5,772,899. Integral passageways for the actuating fluid may be machined or
 otherwise provided in the base 161 in different directions, such as the
 example shown in alternative embodiment of FIGS. 12 (illustrating such a
 passageway 255 for actuating the slave pump) and 13 (illustrating such a
 passageway 226 for actuating the master pump).
 The upper head portion 120 and lower portion 122 can be maintained in
 operative relationship with each other via a wide range of mechanisms.
 Preferably, a threaded nut 128 is retained on the upper head portion 120
 by a retaining flange 129 seated in a groove on the exterior of the upper
 head portion 120, and engages corresponding threads 130 on the outside of
 the lower portion 122. Although the materials for the nut 128 and the
 lower portion 122 can be any of a wide variety, preferably they are
 fabricated from metal to provide a strong, repeatably engagable assembly
 of the head portions 120 and 122. In the preferred embodiment, the threads
 on elements 130 and 128 are relatively coarse, to enable correspondingly
 quick assembly and disassembly of the two portions 120 and 122 from each
 other, for servicing or other maintenance of the first pumping means 20.
 Large threads also are relatively easier to clean than small or fine
 threads.
 The upper head portion 120 also preferably constitutes a monolithic element
 formed or fabricated from a single piece of Teflon.RTM. or similar
 material. As explained herein, this monolithic aspect permits various
 structures and elements to be incorporated directly into the head itself,
 which contributes to the aforementioned benefits of an improved subject
 fluid flow path and reduced number of potentially contaminating
 connections.
 Among other things, the monolithic element 120 preferably includes therein
 an integrally formed or machined valve assembly 140 (see FIGS. 3 and 4).
 The valve 140 is preferably a three-way valve, permitting (as described
 above) selective flow (1) from a fluid source connected to inlet 12
 through the valve 140 to the pumping chamber 18, and (2) from the pumping
 chamber 18 up through the valve 140 and subsequently through the filter
 27. In the preferred embodiments, the valve means 140 includes some
 aspects similar to that disclosed in U.S. Pat. No. 5,261,442, but persons
 of ordinary skill in the art will recognize that any of a wide range of
 specific valve designs will suffice.
 Although the preferred embodiment of the invention incorporates an
 integrally formed three-way valve within monolithic element 120,
 alternative embodiments of the invention may utilize alternative valve
 structures, or may not utilize any valve device. For example, one
 alternative embodiment may utilize a check valve, similar to check valve
 49 described elsewhere herein with respect to the slave pump 30,
 positioned along the fluid flow path between inlet 12 and pumping chamber
 18. As persons of ordinary skill in the art will appreciate, the check
 valve would act to permit the subject fluid to flow into pumping chamber
 18, however would prevent the fluid from flowing back toward the fluid
 source when it is forced from the pumping chamber 18.
 In any case, the preferred fluid flow passes from the pumping chamber 18
 (on its "dispense" stroke) through substantially vertical passages 22 and
 23 in the monolithic element 120.
 Persons of ordinary skill in the art will understand that the valve 140,
 the passages 22 and 23, and the other elements preferably provided in the
 monolithic structure 120 can be formed there by any suitable means,
 including by machining, boring, cutting, or otherwise forming the upper
 head portion 120. By forming those elements integrally with the head
 portion 120, the material of the head portion 120 itself replaces various
 "connections" that were used in prior art devices, and preferably
 simplifies the subject fluid flow path as compared to prior art devices.
 Details of the preferred valve assembly 140 are illustrated in FIG. 4, in
 which the subject fluid is drawn into the system through inlet 12. As
 indicated elsewhere herein, the fitting 13 (similar to other fittings
 mentioned herein) preferably comprises a non-contaminating (e.g.,
 Teflon.RTM. or Teflon.RTM.-coated) flared fitting. Flared fittings are
 commonly used in the semiconductor industry. Typically, a nut such as nut
 205 (FIGS. 9 and 12) is provided adjacent the eventual tubing connection,
 and the tube is flared outward (expanded or stretched) using a special
 tool or process, and is then slipped over the fitting mandrel. Tightening
 the nut holds the flared tubing in place in a sealing relationship.
 One of the many embodiments of this aspect of the invention is illustrated
 in FIG. 12, which shows a nipple 201 having a ring or tongue 202 that fits
 in a sealing relationship into a corresponding groove 203 on the head 220
 (which head 220 corresponds to head 120 in FIG. 3). In the embodiment of
 FIG. 12, the nipple 201 is illustrated as integrally formed with a
 retaining shoulder or plate 204. Screws or bolts 206 (FIG. 9) or other
 methods and apparatus are used to affix the fitting to the head 220. In
 the preferred embodiment, the preferred Teflon material of the head 220
 does not readily and reliably engage a screw's threads directly (such as
 would occur if screws 206 were tapped directly into the Teflon material of
 head 220). Accordingly, one or more rods 207 (FIG. 12) are provided in
 holes 208 (which holes can be "blind" or drilled through the entire head
 220). Persons of ordinary skill in the art will understand that either or
 both ends of the holes 208 will be visible from the outside of head 220 to
 at least some degree (to permit boring the holes 208, inserting the rods
 207, and manipulating those rods as explained below to engage the bolts
 206 therewith), but may be covered, for example, by the plate 209 over the
 integral 3-way valve. Additional holes (not shown) are bored into the head
 220 in a size and location to permit bolts 206 to be inserted into,
 without threadedly engaging, the Teflon head 220. The rods 207 are
 preferably manufactured from stainless steel, and contain cross-drilled
 and tapped holes to accept the screws used to secure the elbow to the lid.
 The end of the bolts 206 are preferably positioned to engage the
 cross-drilled and tapped holes provided in the rods 207, with the threads
 and the position of those holes in those rods 207 sized and located to
 correspond to the bolts 206, so that the bolts 206 can be threadedly
 engaged and tightened therewith. The rods 207 also preferably have one or
 more slots or other structure on their ends so that they can be rotated
 within the holes 208 by a screwdriver or the like, to help align and
 engage the bolts 206 with the rods 207, and thereby tighten the fitting
 onto the head 220.
 Among the many alternative methods of attachment, it is sometimes useful to
 allow the nipple to be rotated or swiveled throughout a complete 360
 degree rotation, especially in combination with elbow fittings attached to
 or formed with the nipple 201. To provide such rotatability, a split ring
 (not shown) or similar annular structure can be provided on the exterior
 of the fitting near the head 220, and a sleeve or plate similar to plate
 204 can be provided to engage the split ring or shoulder. The sleeve or
 plate similar to plate 204 can then be engaged with the head 220 as
 described above, and the swivel adjustment can be performed prior to
 tightening the screws or bolts 206, or preferably even after the screws or
 bolts are tightened.
 To permit the pumping chamber 18 to fill with process fluid (for subsequent
 pumping through the rest of the system 10), a central plunger assembly 142
 of the valve 140 is depressed in the direction of arrow A in FIG. 4 (via
 computer-controlled air actuation, not shown, pushing on the end 144 of
 plunger assembly 142 through the opening 146--see the discussion below of
 element 246 in the alternative embodiment of FIG. 10). In the preferred
 embodiment, the air actuation of the plunger assembly 142 is preferably
 controlled by a diaphragm, but alternatively can be controlled by pistons.
 Indeed, an actuator (such as a separate rod or plunger, for example, not
 shown) or other mechanical structure can be provided to actuate the
 plunger assembly 144/142. In any case, the actuating pressure must
 overcome the spring force exerted by spring 148, and that spring 148 keeps
 the valve 140 in a default position of permitting flow from the pumping
 chamber 18 through the valve 140 to the filter 27. By depressing the
 plunger 142 and compressing the spring 148, fluid flow is permitted
 through the inlet tubing 12 through the vertical channel 22 and into the
 pumping chamber 18. When the pressure is released from the end 144 of the
 plunger 142, the spring 148 forces the plunger back into the position
 shown in FIG. 4, permitting the aforesaid fluid communication from the
 pumping chamber 18 through the valve 140 to the filter 27.
 Further enabling this valve action are the preferably kidney-shaped
 passages 152 (shown in FIGS. 3 and 4) and 154 (shown only in FIG. 3, due
 to the cross section location of line 4--4). Preferably, the passage 152
 opens toward the viewer as one looks at FIG. 3, while the passage 154
 opens in the opposite direction (away from the viewer, or toward the
 "back" side of FIG. 3). The preferred kidney shapes 152 and 154 enlarge
 what might otherwise be a constriction in the fluid flow, improving the
 performance of the system 10 generally but especially with respect to
 processing shear-sensitive and/or high viscosity fluids. Referring to
 FIGS. 3 and 4, persons of ordinary skill in the art will understand that
 the "dispense" stroke of the first diaphragm 124 forces the subject fluid
 up passage 22, through the central space 147 not occupied by the plunger
 142, into the annular passage 149 and thereafter into the rearward-facing
 kidney-shaped opening 154 and up through passage 23 to the filter 27.
 For applications in which the subject fluid is to be filtered, the upper
 head portion also preferably includes an integrally molded or machined
 filter housing or chamber 160. The chamber 160 preferably includes a
 removable lid member 162, to permit maintenance or other access to the
 filter element 27. For compactness and the non-contaminating and other
 benefits discussed herein, the lid member 162 is also preferably
 manufactured or fabricated from a monolithic block of Teflon.RTM. or
 similar material. An O-ring or similar sealing means 166 is preferably
 provided between the lid member 162 and the upper body portion 120, to
 prevent leakage at that joint. A nut 164 (similar in concept to nut 128 at
 the lower exterior of the first pumping means) preferably threadedly
 attaches the lid member to the upper body portion 120, and is readily
 removable via relatively coarse threads. In order to provide an improved
 seal at that joint, however, and to extend the life of the joint and its
 components, the nut 164 is preferably also formed from polypropylene,
 Teflon.RTM., or some similar plastic material. Among other things, this
 ensures that the life of the threads at that joint is longer than might
 occur if, for example, the nut were formed of metal and thereby "ate" into
 the corresponding Teflon.RTM. threads formed on the upper body portion
 120.
 In the alternative embodiment of FIGS. 9-14, the lid member 262
 (corresponding to lid member 162 in FIGS. 1-8; many of the "200" series
 numbers in FIGS. 9-14 have a similar correspondence to the "100" numbers
 in FIGS. 1-8) extends downwardly into the chamber 260. The O-ring 266 can
 then be positioned in an outer annular channel 256, which can help prevent
 leakage (as compared to the "face-seal" configuration of the O-ring 166 in
 FIGS. 1-8) if, for example, the entire lid member 262 and nut 264 "move"
 vertically upwardly during pressurization of the system. The likelihood of
 any such movement can be affected by, among other things, the material
 from which the nuts 164 or 264 are formed (plastic nuts might permit more
 such "movement").
 The filter element 27 can be any suitable filter media in any suitable
 configuration. Among the many suitable filters 27 are ones manufactured by
 Millipore Corporation, under the brand names and model numbers PI-250
 Cartridge (catalog number DZUP CZI K1) and Wafergard F Cartridge (catalog
 number WGFG 40H P1). Preferably, the filter means is integrally positioned
 within the first pump 20, thus reducing the overall length of the flow
 path of the fluid or at least the number of connections required within
 the flow path. To provide the desired non-contaminating performance, the
 filter 27 is preferably coated or fabricated from Teflon.RTM. or similar
 material.
 Filter 27 is preferably adapted to filter the subject fluid as it passes
 from the vertical passage 23 to a flow path exit passage 165 formed in the
 lid member 162. To ensure desired flow from vertical passage 23 into the
 filter chamber, the preferred embodiment includes one or more raised
 portions 170 (see FIGS. 3 and 5) to space the filter element 27 off the
 bottom of the filter chamber. In this manner the filter means 27 does not
 cover and block fluid flow from the top of the passage 23 into the filter
 chamber. In the preferred embodiment, these portions 170 are formed by
 "leaving" segments of the monolithic block 120 during machining of the
 filter chamber therein. As illustrated, four such portions 170 are equally
 spaced about the central opening 23, although a wide range of other
 suitable configurations or other elements (not shown) could be used.
 To further ensure desired "unrestricted" flow from vertical passage 23 into
 the filter chamber, the preferred embodiment also includes a countersunk
 or tapered portion 24 (FIGS. 3 and 5).
 As with the passages 22 and 23 in the upper body portion 120, the exit
 passage 165 in the lid member 162 can be formed or fabricated in any
 suitable manner, including drilling or similar machining. The passage 165
 provides a flow path through the lid member 162 for the subject fluid, and
 is preferably connected to an elbow 167 (persons of ordinary skill in the
 art will understand that the exit flowpath can be any suitable path, but
 preferably does not direct the flow downwardly). Although the various
 fittings and other components can be assembled to each other in any
 suitable manner, a preferred method and structure for many of the
 attachments is best illustrated in FIGS. 12 and 13, and as described
 elsewhere herein. Among other things, those Figures illustrate preferred
 attachments of fittings within the system (such as elbow 167) to various
 Teflon components (such as the major "block" elements fabricated from
 Teflon). The elbow 167 is preferably connected at its other end to another
 Teflon.RTM. flare fitting 168 and tubing 169, and then on to the second
 pumping means of the system 10, as discussed elsewhere herein. Tubing 169
 is preferably fabricated from or coated with Teflon.RTM. or a similar
 material.
 The lid member 162 also preferably incorporates a vent valve assembly 36,
 FIG. 6, operatively connected by machined passage 174 to a relatively high
 point in the filter chamber (corresponding alternative elements 236 and
 274 are illustrated, for example, in FIGS. 12 and 13). In the preferred
 embodiment, the vent valve is all Teflon.RTM., and is a two-way, normally
 closed valve that can be used to selectively vent gas from the process
 fluid. One of the many valves suitable for this purpose is manufactured by
 Furon Company (currently doing business at 3340 East La Palma Avenue,
 Anaheim, Calif. 92806, USA, which is the same Furon referred to in other
 parts of this description), and is illustrated in U.S. Pat. No. 5,575,311.
 Persons of ordinary skill in the art will understand that connecting this
 vent valve to a "high" point within the system permits the vent valve 36
 to collect and vent undesirable gases that may be entrained within the
 subject fluid. Moreover, any such gas is likely to vent through passage
 174 (or passage 274 in the embodiment of FIG. 12) as opposed to the more
 central passage 165 in the lid member 162 because the gas does not have to
 pass through the filter element 27 in order to get to the passage 174 (in
 contrast to having to do so to reach passage 165). In the preferred
 embodiment of the invention, the valve is automatically actuated by the
 pump controller and is user programmable. In addition, the valve is
 preferably and typically opened either during the beginning or end of the
 filtration cycle for a short period of time (preferably on the order of
 seconds). Vent 36 preferably includes a spring 37 and related adjustments
 by which its relief pressure can be set, enabling it to also function as a
 safety valve or relief valve to ensure that the pressure on the subject
 fluid does not exceed a certain level, or to provide relief if the filter
 element 27 becomes clogged, etc.
 For applications in which a second pumping means is desired (for example,
 in applications such as some discussed in the aforementioned U.S. Pat.
 Nos. 5,167,837, 5,516,429, and 5,772,899), a slave or second pump member
 30 (FIG. 7) is preferably provided. Many aspects of the preferred pump 30
 are similar to those of the first pumping member 20 discussed above,
 including a pumping chamber 44 having a diaphragm therein actuated in a
 precisely controlled manner by a stepper assembly (not shown in FIG. 7,
 but illustrated in FIG. 2 as assembly 190, which can move actuating fluid
 through port 55) or similar mechanism.
 The slave pump 30 can be positioned in a wide variety of locations with
 respect to the master pump 20, but is preferably sufficiently "high" that
 the fluid flow path trends upwardly through tubing 169 between the pumps
 20 and 30. Among other things, the tubing 169 preferably at least does not
 travel downwardly as the fluid moves from the first pump 20 to the second
 pump 30, because such a downward path might entrap gas within that section
 of the system 10. Among the many alternative embodiments (not shown), the
 second pump 30 could even be positioned "directly" over the first pump 20,
 resulting in the tubing 169 or other passage or connection between the
 pumps 20 and 30 being substantially vertical (and thereby having virtually
 no risk of gas entrainment therein). To facilitate manufacture of the
 system 10, however, as well as its assembly and maintenance, the preferred
 embodiment positions the first pumps 20 and 30 with respect to each other
 as best illustrated in FIGS. 1 and 2.
 The slave pump 30 preferably includes a monolithic upper portion 42 formed
 of Teflon.RTM. or similar material, whose monolithic nature provides
 similar opportunities for improved flow and reduced contamination as
 discussed elsewhere herein. Preferably, a tee path is drilled or otherwise
 machined or formed in the upper portion 42, and includes a substantially
 vertical passage 45 teed to another passage 47. That passage 47 preferably
 receives the fluid flow from tubing 169, after it passes through a
 preferred further Teflon.RTM. flare fitting 48 (or other non-contaminating
 connection) and a check valve 49 integrally mounted into the upper portion
 42.
 Among other things, the check valve 49 is preferably formed of Teflon.RTM.
 or similar non-contaminating material, and prevents the pumping/dispense
 stroke of the pumping chamber 44 from forcing the subject fluid back out
 passage 47 and toward the filter 27. Instead, the check valve 49 causes
 the pumping/dispense stroke of the pumping chamber 44 to force fluid
 further upward through passage 45 and thereafter to elbow 51 and
 Teflon.RTM. flare fitting 52 (the comments above regarding elbow 167 and
 fitting 168 on the first pumping member 20 apply with equal force to elbow
 51 and fitting 52). One of the many suitable valves usable as check valve
 49 is currently marketed by Furon as their part number MCV 246.
 For strength and economy, the lower portion 53 of the second pumping member
 30 is preferably fabricated from stainless steel, aluminum, or some other
 metal, and the retaining nut 54 is likewise fabricated from metal. Persons
 of ordinary skill in the art will understand, however, that any of a wide
 variety of materials can be used for those elements without departing from
 the scope of the invention.
 As indicated above, the dispense of fluid out tubing 46 is preferably
 directed to yet another non-contaminating three-way valve (not shown, but
 graphically illustrated in FIG. 8 as element 99), by which the subject
 fluid can be selectively directed back to the source 60 or to be dispensed
 on a substrate or other microelectronic chip or device-in-process (not
 shown). In the preferred embodiment, the three-way valve 99 is a
 stand-alone valve (in contrast to the integrally-formed valve 140 within
 first pumping member 20) and is attached to tubing 46 and a return tubing
 (not shown, but illustrated in FIG. 8) via the aforementioned
 non-contaminating Teflon.RTM. flare fittings. The three-way valve means 99
 preferably is a zero displacement valve, such that none of the subject
 liquid is displaced when the valve is actuated. As indicated above, and
 among other things, the preferred valve reduces or eliminates the
 likelihood that operating the valve will displace fluid (such as
 displacing it from the dispense line), which displacement could adversely
 affect the accuracy of dispense or other aspects or performance of the
 system.
 Persons of ordinary skill in the art will also understand that the
 alternative embodiment of FIGS. 9-14 includes further benefits. Among
 other things, the second pump 230 is slightly higher relatively to the
 first pump than in the embodiment of FIGS. 1-8, and the tubing 269 between
 the pumps is provided in an uncoiled path. The various fittings on the
 pumps by which the subject fluid enters and exits the pumps are redirected
 to facilitate use in possible alternative locations and installations. In
 FIG. 10, a fitting 246 is provided to facilitate the air actuation of the
 preferred integral three-way valve.
 FIG. 14 also illustrates preferred pressure transducers 285 and 295,
 associated with the first and second stepper assemblies 280 and 290,
 respectively. Two lower units (shown as elements 293 in FIG. 10, and
 corresponding to upper units 283 in both FIGS. 10 and 14), represent the
 servo-motor assembly, but as indicated above, are not shown in FIG. 14 to
 permit better viewing of the transducers 285 and 295. Persons of ordinary
 skill in the art will understand that the transducers are configured to
 sense the pressure within the actuating fluid on the respective first and
 second stepper assemblies 280 and 290, and transmit same to a computer
 control mechanism (which computer control is preferably capable of sensing
 and operating other inputs and aspects of the assembly 10). The
 transducers can be utilized for a wide variety of purposes, including
 (without limitation): monitoring the recharge (negative) pressure;
 indicating the need for servicing or replacing the filter (such as by
 monitoring the filter pressure or differential pressure across the
 filter); monitoring the dispense pressure or the entire pressure cycle
 (which can be used for advanced process control); and other functions.
 The apparatus and methods of my invention have been described with some
 particularity, but the specific designs, constructions and steps disclosed
 are not to be taken as delimiting of the invention. Obvious modifications
 will make themselves apparent to those of ordinary skill in the art, all
 of which will not depart from the essence of the invention and all such
 changes and modifications are intended to be encompassed within the
 appended claims.