Patent Grant
7025234
1. Field of Invention
The present invention generally relates to apparatus and method for dispensing a process liquid characterized by a high viscosity and a short shelf life.
2. Related Art
Semiconductor manufacturing processes frequently employ process liquids of high viscosity, such as polyimides (typically having a viscosity of 250–35,000 centipoises), which exhibit a good combination of thermal stability, mechanical toughness and chemical resistance and can be used as protective overcoats, interlayer dielectrics, or passivation layers in microelectronic applications. Due to their high viscosity, these process liquids are usually dispensed from pressurized storage and dispensing vessels, by special dispensing pumps in conjunction with large diameter tubing (e.g., 0.9525 cm, 0.375 inch diameter).
A recirculation loop downstream of the dispensing pump is usually provided to keep the high viscosity process liquid in continuous fluidic motion at a desired flow rate. Such a recirculation loop reduces solidification of the liquid (e.g., gel slug formation) inside the dispensing lines, prolongs the shelf life of such liquid, and provides a means for purging air out of the dispensing lines. The recirculation loop usually comprises a three-way dispensing/recirculating valve, a recirculating line, and a recirculating probe coupled to the fluid vessel, for re-circulating the high-viscosity process liquid back into such vessel.
Conventional recirculation probes comprise an output flow path connected to an output port, and a return flow path connected to a recirculating port. A process liquid flows out of the fluid vessel via the output flow path and the output port, and re-circulated process liquid flows back into the fluid vessel via the recirculating port and the return flow path. Typically, the cross-sectional flow area of the return flow path is much smaller than that of the output flow path. Therefore, when the output liquid volume is substantially equal to the re-circulated liquid volume (as usually occurs when purging gas out of the dispensing lines), such difference in cross-sectional flow areas of the output and return flow paths causes an imbalance of discharge pressures in the dispensing line and in the recirculating line. This imbalance unduly burdens the dispensing pump and the dispensing/recirculating valve and causes the pump and the valve to wear out prematurely.
Moreover, conventional recirculation probes feature separate tubing for the output flow path and the return flow path. Such separate tubing configuration does not effectively use the limited cross-sectional area of the opening of the fluid storage and dispensing vessel.
Further, the return flow path of conventional re-circulation probes terminates right below the neck portion of the fluid vessel, in order to minimize the inner surface area of the return flow path and to reduce the head losses caused by the flow resistance of the inner surface of the return flow path. However, such design leaves a free space between the end of the return flow path and the liquid surface within the fluid vessel, and the re-circulated liquid therefore drips in a free-fall manner from the return flow path into the fluid vessel, causing liquid turbulence and deleterious formation of air bubbles in the fluid vessel.
It is therefore one object of the present invention to reduce or eliminate the pressure imbalance between the dispensing line and the recirculating line, so as to prolong the useful life of the dispensing pump and the dispensing/recirculating valve.
It is another object of the present invention to effectively use the limited cross-sectional area of the opening of the fluid storage and dispensing vessel, and to concurrently maximize the effective flow area of the output and return flow paths.
It is still another object of the present invention to provide a smooth flow of the re-circulated fluid back into the fluid storage and dispensing vessel, so as to reduce liquid turbulence and formation of air bubbles in such vessel, without significantly increasing the inner surface area of the return flow path.
It is a still further object of the present invention to provide a liquid recirculating system with changeable liquid outflow ports and/or recirculation ports, and to enable sealed dispensing of high-viscosity liquids that eliminates exposure of such liquids to airborne contaminates and eliminates exposure of personnel to the hazardous fumes of such liquids.
Other objects and advantages will be more fully apparent from the ensuing disclosure and appended claims.
The present invention significantly reduces or eliminates the pressure imbalance between the output flow path and the return flow path, by providing an apparatus for dispensing a liquid from a fluid storage and dispensing vessel to a liquid dispensing system. Such apparatus comprises a recirculating probe and a connector for coupling said recirculating probe to an opening of the fluid storage and dispensing vessel, and the recirculating probe comprises:
When the return flow path has a cross-sectional area substantially equal to that of the output flow path, the discharge pressures in the output flow path and the return flow path are substantially the same, so the pressure imbalance between the output flow path and the return flow path is reduced or eliminated.
Another aspect of the present invention relates to an apparatus for dispensing a liquid from a fluid storage and dispensing vessel to a liquid dispensing system. Such apparatus comprises a recirculating probe and a connector for coupling said recirculating probe to an opening of the fluid storage and dispensing vessel, while the recirculating probe comprises:
Such concentric design maximizes the effective flow area of the output and return flow paths within the dimensional constraint of the vessel opening.
In a preferred embodiment of the present invention, the return flow path is defined and bounded by an outer wall of the dip tube, so that when the re-circulated liquid flows from the recirculating port into the return flow path, the re-circulated fluid contacts the outer wall of the dip tube, and flows down such dip tube into the fluid storage and dispensing vessel. In such manner, the dip tube concurrently functions as a flow-directing tube for the re-circulated liquid flow. The re-circulated liquid flow directed by the dip tube according to the present invention demonstrates significantly reduced splashing or turbulence and minimizes formation of air bubbles in the liquid, in comparison with the free-fall dripping of the re-circulated liquid in the conventional recirculating probes.
In another preferred embodiment of the present invention, the recirculating probe comprises detachable output port and return port, for ready replacement of damaged ports, and ease of cleaning of the flow paths of such recirculating probe.
In a still further embodiment of the present invention, the recirculating probe comprises two O-ring seals, one disposed between the dip tube and the output port, and the other disposed between the recirculating probe and the opening of the fluid storage and dispensing vessel. This arrangement completely seals the output flow path and the fluid vessel, eliminates exposure of the dispensed liquid to airborne contaminates, and prevents exposure of personnel to the hazardous fumes of such dispensed liquid.
A further aspect of the present invention relates to methods of dispensing a high-viscosity liquid from a fluid storage and dispensing vessel, using the apparatuses described hereinabove.
As used herein, the term “high-viscosity liquid” refers to a liquid that has a viscosity of at least 50 centipoises. More preferably, such liquid has a viscosity of at least 100 centipoises, and most preferably at least 1000 centipoises. For example, the high-viscosity liquid may have a viscosity in a range of from about 50 to about 100,000 centipoises. The liquid viscosity values as set out herein are measured at 25° C. by a Brookfield viscometer, using a No. 2 spindle and at a shear rate of 300 rpm).
The high-viscosity liquid may be a process liquid useful in a semiconductor manufacturing process, such as polyimide resin. Alternatively, such liquid may be a process liquid useful in pharmaceutical processes, such as liquids used in DNA synthesizers, peptide synthesizers, and other liquid reagents widely used in industrial processes. The exemplary liquids listed here are merely illustrative and are not intended to limit the broad scope of the present invention.
Additional aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.
There are several problems related to the conventional design of the recirculating probe.
First, as shown in
In order to eliminate such pressure imbalance and to prolong the useful life of the dispensing pump and the dispensing/recirculating valve, the present invention provides a recirculating probe 40, as shown in
A primary advantage of the recirculating probe as shown in
Therefore, the output flow area OA, which is the cross-sectional area of the output flow path 52, equals
The return flow area RA, which is the cross-sectional area of the return flow path 60, equals
According to the present invention, RA is designed to be substantially equal to OA (i.e., RA=100% OA with ±5% deviation), for purpose of minimizing pressure imbalance between the dispensing line and the recirculating line and reducing wear on the dispensing pump and the dispensing/recirculating valve.
In an illustrative preferred embodiment of the present invention, 0.889 cm, 0.35 inch≦D1≦1.143 cm, 0.45 inch, preferably D1=0.9525 cm, 0.375 inch, 1.143 cm, 0.45 inch≦D2≦1.397 cm, 0.55 inch preferably D2=1.27 cm, 0.5 inch, and 1.524 cm, 0.60 inch≦D3≦1.651 cm, 0.65 inch, preferably D3=1.5875 cm, 0.625 inch. Preferably, both the output flow area and the return flow area are approximately 0.7122 cm2, 0.1104 square inch.
It is also within the scope of the present invention to use output flow path and return flow path configurations that are not concentric, as long as the output flow area is substantially equal to the return flow area.
A second independent advantage of the present invention relates to the preferred concentric design of the output flow path and return flow path, which maximizes the effective flow area of such paths for a given total cross-sectional area of the vessel opening. The conventional non-concentric design of the output flow path and return flow path, as shown in
In the conventional recirculating probe 10 as shown in
In order to overcome the above-described problems, the recirculating probe 40, as shown in
When re-circulated liquid enters the return flow path 60 from the recirculating port 58, such re-circulated liquid annularly spreads around the outer wall of the dip tube 50 and flows smoothly down the outer wall of the dip tube 50 into the fluid vessel 42. Thus, the dip tube 50 performs dual functions in the present invention: (1) it defines the output flow path 52 for flowing liquid 48 out of the fluid storage and dispensing vessel 42; (2) it directs the flow of re-circulated liquid back into the fluid storage and dispensing vessel 42. As shown in
The re-circulation probe of the instant invention may be manufactured from any polymeric material having characteristic high purity and good thermal stability. Preferably, the recirculation probe is manufactured from Teflon® PFA 445 HP polymer available from DuPont Fluoroproducts, Wilmington, Del. The Teflon® PFA 445 HP polymer is characterized by high purity and good thermal stability (having a melting point of from about 302° C. to about 310° C., which enables melt extrusion of the perfluoroalkoxy resin at temperatures from about 350–400° C., preferably at a temperature of about 390° C.). Use of the high purity PFA 445 polymer for the recirculation probe body significantly reduces contamination of the processing liquid.
Regarding the fluid storage and dispensing vessel, the present invention utilizes a “bag-in-a-bottle” design, for easy recycling of such vessel and for non-contact pressurization of the liquid in such vessel.
Specifically, the high-viscosity liquid 48 is stored in a liner 43 located in the fluid storage and dispensing vessel 42. Between the liner 43 and the fluid vessel 42, there presents a liquid-free space, to which pressurized gas can be introduced. Because the liner 43 is fabricated of a relatively flexible and deformable material (such as an elastomer or polymer), the pressurized gas so introduced indirectly applies pressure to the liquid 48 through the liner 43 to facilitate dispensing of the liquid 48, but without direct contact to the liquid 48 (i.e., the pressurized gas is isolated from the liquid 48 by liner 43 ). Therefore, the present invention effectively avoids contamination of the process liquid by the pressurized gas, and reduces outgassing and formation of micro-bubbles due to dissolution of the pressurized gas into the liquid under high pressure.
The liner 43 can be fabricated of any deformable elastomeric or polymeric material that has sufficient thermal stability and does not deleteriously interact with the liquid contained therein. Preferably, the liner is made of one or more fluoropolymers, such as perfluoroalkoxy-based polymers and polytetrafluoroethylene resins, etc. Suitable liner materials include but are not limited to perfluoroalkoxy resin (PFA), PTFE, Nylon, Polyethylene, ECTFE Poly/nylon, polyethylene, and PFA/PTFE, and combinations thereof.
The pressurized gas as described hereinabove can be introduced from an external pressure source (not shown) into the storage and dispensing vessel 42, via a pressure assist port. After the liquid 48 is dispensed, the internal pressure inside the container, where chemical resides can be reduced by disconnecting the quick disconnect pressurization fitting as shown in
A pressure relief valve on the container (not shown) functions to prevent an overpressure condition within the bottle (or between the outside layer of the liner and the inside wall of the bottle) when air pressure is being applied to the liner to help in the dispensing of the chemical.
The no-contact pressure dispensing of liquids, as described hereinabove, reduces the mechanical load on the dispensing pump of the liquid dispensing system 56 and prolongs the useful life of such pump, without increasing the risk of contamination of the process liquids.
In another preferred embodiment of the present invention, the output port 54 is detachably coupled to the dip tube 50 by the output flowpath fitting which may be threaded into the recirculation probe body and an integral flowpath fitting locking collar 53, and/or the recirculating port fitting 58, is detachably coupled to the return flow path 60 by a nut 47, so that either or both of the output and recirculating port fittings can be detached from the recirculating probe 40. Such detachable coupling allows easy and quick replacement or removal of the output and/or recirculating ports, e.g., in case that such ports are damaged and need to be replaced, or when it is necessary to clean the flow paths inside the recirculating probe 40.
The replaceable output port fittings and recirculation port fittings provide for built in fitting modularity as they are readily changeable for easy hook up of varying size diameter tubings. Such modularity provides for significant savings to the user as one re-circulation probe accommodates tubing sizes such as ¼ O.D., ⅜ O.D., or ½ O.D and combinations thereof.
The integral locking collar prevents rotation of the output fitting by having a top half of the collar fitting tightly over the hex end of the fitting, and the bottom half of the collar being “pinned” into the top surface of the recirculation probe body. This locking is achieved with out the need for additional tools or parts. It relies on close tolerance “slip fits” for all mating parts.
The sealing connection between the output port fitting 54 and the diptube 50 is made when the tapered/radiused mating surfaces of each item come into contact with each other. This normally precludes any liquid from traveling up the threaded portion of the output port fitting 54 and leaking from the recirculation probe body. Optionally; a secondary seal such as an O-ring 51 may be incorporated into the sealing connection to further prevent leakage of liquid 48 from such connection.
In the embodiment shown in
A pressure-assist port 92 is employed in the recirculating probe 70 for introducing pressurized gas into the space between the outer surface of liner 94 and inner surface of the fluid vessel 72, to facilitate delivery of high-viscosity liquid 82.
Another embodiment of the present invention allows the return flow path and output flow path to have equal cross-sectional areas, without being concentric. For example, the output flow path can have a semi-circular shaped cross-sectional area, while the return flow path can have a complementary semi-circular cross-sectional area of equal or substantially equal size. Any suitable geometry can be used to provide the re-circulate return path with an effective cross-sectional area equal to or greater than that of the output flow path, as readily determinable by a person ordinarily skilled in the art, on the basis of the disclosure herein.
The recirculating probe of the present invention provides a simple and cost-effective way for purging gas out of the dispensing line of a process liquid, without inducing significant waste of such process liquid. It also helps to maintain continuous flow motion of a high-viscosity process liquid, such as polyimide and other viscous resins, so as to prevent gel slug formation inside the dispensing line of such process liquid.
Although the invention has been variously disclosed herein with reference to illustrative embodiments and features, it will be appreciated that the embodiments and features described hereinabove are not intended to limit the scope of the invention, and that other variations, modifications and other embodiments will suggest themselves to those of ordinary skill in the art. The invention therefore is to be broadly construed, consistent with the claims hereafter set forth.
This claims the priority of U.S. Provisional Patent Application No. 60/345,043 filed Oct. 20, 2001 in the names of Kevin T. O'Dougherty
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| Number | Date | Country | |
|---|---|---|---|
| 20030075566 A1 | Apr 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60345043 | Oct 2001 | US |
