Dispensing – Processes of dispensing
Utility Patent
1998-09-22
2001-01-02
Kaufman, Joseph A. (Department: 3754)
Dispensing
Processes of dispensing
C222S061000, C222S064000, C222S318000, C222S386500, C222S399000
Utility Patent
active
06168048
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the distribution of liquid process chemicals from a bulk source or container to one or multiple end users, especially for the distribution of ultrapure liquid chemicals to semiconductor wafer and electronic chips manufacturing users.
2. Related Art
In many manufacturing processes various chemicals are required to be distributed from a bulk source to the point-of-use without contamination and deterioration of the chemical qualities. For example, in semiconductor wafer and computer chip manufacturing processes, ultrapure chemicals are needed for cleaning, etching, and surface treatment, and the like. These chemicals may include some caustic, acids, and organic liquids, such as ammonium hydroxide, sodium hydroxide, hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, hydrogen peroxide, isopropyl alcohol, tetramethylammonium hydroxide, chemical slurry, and mixtures of the above or different chemicals. The chemicals must be at the user's point regardless of the continuous or intermittent usage. The chemicals must also be maintained at high purity level and without being contaminated during the delivery and distribution from bulk sources.
A few methods have been provided for distributing the chemicals so far. One of the methods is the so called “vacuum-pressure” distribution disclosed by Johns (WO92/05406), Magnasco and Viale (U.S. Pat. No. 4,524,801), Geatz (U.S. Pat. No. 5,148,945), Bernosky et al. (WO94/21551, U.S. Pat. No. 5,370,269), and Ferri and Geatz (U.S. Pat. No. 5,330,072 and U.S. Pat. No. 5,417,346). The basic idea is that the chemical to be delivered is withdrawn from a bulk chemical source by virtue of the vacuum inside a pressure vessel created with a vacuum pump and then distributed to the user by pressurizing the chemical with inert gas. The chemical can be distributed continuously with more than two systems in parallel and to a user away at a far distance by operating at a high pressure. However, this “vacuum-pressure” method has several drawbacks. First, the chemical can be contaminated by the leakage of ambient air into the system because of the negative pressure inside the system. Another drawback is that the vacuum pump used to create vacuum has high down time because of the corrosion of the pump components by the chemical vapor and droplets. Yet another drawback is that the exhaust of the inert gas with the chemical vapor and droplets from the vacuuming procedure produces an environmental concern. This exhaust may be saturated by the chemical, especially in the distribution of high vapor pressure chemicals. Since the inert gas directly contacts the chemical at a high pressure, the gas will dissolve in the liquid phase and become bubbles in the chemical. The bubbles may result in a serious quality problem in the wafer and electronic chips manufacturing. For example, they may attach to the wafer surface and create a non-wetted spot on the surface.
Another method to distribute the chemical to the end users is the so called collapsible container method disclosed by Ramsay (U.S. Pat. No. 5,570,815). With this method, the chemicals to be distributed must be filled within a container with flexible walls. This container is then positioned inside a pressure vessel and squeezed with a high pressure gas. Therefore, the chemical is pushed out of the container and delivered to the users. The chemical does not directly contact with the high pressure gas as with the vacuum-pressure method. However, the chemical quantity in the container is difficult to be monitored, and therefore, it is difficult to continuously deliver the chemical. Another drawback of this method is that the distribution system with this method can not be controlled automatically. Further, the collapsible container can be easily broken especially at the fixing points under the high pressure because of the disjoining force of the high pressure gas.
Another widely practiced method is the pumping delivery method. A positive displacement pump, such as a double diaphragm pump driven by air or gas, is used to deliver the chemical from a bulk source or an intermediate container to the end users. As the technical development, the lift force of this type of pump has been improved. For example, a Yamada diaphragm pump can operate at the pressure up to 50 PSI. This lift force, however, is still not high enough for many applications, especially for the practice of viscous chemicals and long distance delivery. Another drawback is the contamination of the impurities shed from the components of the distribution system due to the flow pulsation produced by the pump.
Another method is the so called pump-pressure distribution. A pump is employed to deliver the chemical from a bulk source to a pressure vessel. The chemical in the vessel is then pressurized with high pressure gas to be delivered through a distribution system to the end users. Some of the above mentioned drawbacks with the vacuum/pressure and the pump delivery methods still exist. First, the gas directly contacted with the chemical will dissolve in the chemical and become bubbles that result in serious problem on the wafer or micron chip surfaces. Second, the impurity shedding from the filters and other components by the pulsation upon the start of a pump will contaminate the ultrapure chemicals.
SUMMARY OF THE INVENTION
Methods and apparatus for distributing process liquid chemicals, preferably ultrapure liquid chemicals, are disclosed. Chemical from a bulk source is pumped into a pressure chamber between the internal wall of a pressure vessel and a balloon-like gas bag installed inside the pressure vessel, and then pressurized with the balloon while it is filled with high pressure gas for distributing to one or multiple end users through a series of conduits and flow control devices. The use of a balloon avoids direct contact of the high pressure gas with the liquid chemical, and therefore, the possible contamination and dissolution of the gas in the chemical. The exhaust from the balloon inside the pressure vessel during de-pressurization has no environmental concern. A pump used to deliver the chemical from the bulk source to the pressure chamber assures the system always in a positive pressure to eliminate the contamination by ambient air leaking into the system and the downtime due to the failure of a negative pressure system. Use of optional duplicate pressure chamber provides the option for continuously distributing the chemical to end users from one chamber while another chamber is in filling operation mode. The chemical can recirculate through a loop back to the bulk source before going to the pressure chamber for any quality reason. The chemical can also re-circulate from the pressure chamber either back to the bulk source or to another pressure chamber. One of the other re-circulation loops may be used for re-circulating the redundant chemical from the user station to the bulk source. The distribution apparatus of this invention is preferably integrated into a cabinet and preferably controlled with an electronic control system.
With the inventive aspects disclosed in this application, many of the problems associated with previous chemical transferring and/or distribution systems and methods have been solved. Briefly, this invention uses one or more pressure vessels having installed therein on its inside a balloon of flexible and non-expandable wall to smoothly and continuously deliver a chemical to any end user without contamination and gas dissolution. Since the balloon installed inside the pressure vessel isolates a high pressure gas from the chemicals, gas dissolution in the chemical and the resulted gas bubble problems are effectively eliminated. Further, contaminants in the high pressure gas which fills the balloon will not be transferred into the chemical and the extremely toxic chemical will not be transferred into the gas to be exhausted as a serious environmental issue. Unlike the vacuum/pressure system, the contamination by the am
Vigor Xavier
Xu Mindi
American Air Liquide Inc.
Kaufman Joseph A.
Wendt Jeffrey L.
LandOfFree
Methods and systems for distributing liquid chemicals does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods and systems for distributing liquid chemicals, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods and systems for distributing liquid chemicals will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2514813