Cleaning and liquid contact with solids – Processes – Using sequentially applied treating agents
Reexamination Certificate
1999-10-11
2001-08-07
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
Using sequentially applied treating agents
C134S021000, C134S030000, C134S031000, C134S095200, C134S095300, C134S100100, C134S102200, C134S198000, C134S902000, C034S061000, C034S079000, C034S202000, C034S218000, C034S221000, C034S164000, C034S340000, C034S342000, C034S401000
Reexamination Certificate
active
06270584
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improvements in drying and cleaning of manufactured objects, including electronic components, using aerosols created by sonic or ultrasonic means.
BACKGROUND OF THE INVENTION
Objects that are being manufactured using processes involving application of liquids and other fluids often require that the parts be thoroughly dried before the manufacturing process can continue. For example, in fabrication of integrated circuits, doping, photomasking, etching and passivation processes often require application of particular liquids at one stage and removal of liquid residues before the next stage proceeds. Drying and removal of these liquid residues must be complete, but the drying process should, ideally, occur in a relatively short time interval and with expenditure of a minimum of energy and chemicals to implement the drying process.
Several workers have disclosed methods for drying parts, including integrated circuits, by use of heated or superheated gases. These approaches heated or superheated gases or direct beam irradiation to dry an object surface; or they use cooperative action by an ultrasonic beam and an active chemical bath to remove contaminants from, or to apply a desired material to, an object surface. These approaches are complex, usually require operation at high temperatures, often require processing times of several minutes, and often require use of specially resistant chamber walls for the processing chamber.
What is needed is a method and associated apparatus for drying and cleaning objects in a manufacturing process that works well at room temperature and is simple, that is demonstrably complete, with no significant residues, that can be accomplished in times as short as one minute, that can be performed in a chamber with chamber walls made of almost any material, and that requires use of only a very small amount of a drying agent, with minimal expenditure of energy, particularly thermal energy. Preferably, the process should be performable over a wide range of temperatures, and should be easily scalable to any size surface.
SUMMARY OF THE INVENTION
The needs are met by the invention, which provides improvements for a method and associated apparatus for drying and/or cleaning objects by use of a small amount of a low surface tension liquid plus (optionally) brief application of a recyclable cleaning agent. In one embodiment, the objects to be dried are submerged in a rinse liquid, such as water, in a chamber. The rinse liquid surface is covered with a very thin film of a low surface tension selected liquid, such as isopropyl alcohol (“IPA”), formed from an aerosol created by sonic or ultrasonic vibrations of a small stream of the selected liquid. Other suitable liquids include ethyl alcohol, methyl alcohol, tetrahydrofuran, acetone, perfluorohexane, hexane and ether. The thin film is continually replenished as needed, and the rinse liquid covering the objects to be dried is slowly drained. As the rinse liquid and thin film drain, the selected liquid briefly contacts the surfaces of the objects and removes water residues by a “chemical squeegeeing” process that is discussed later. Optionally, the objects can be subjected to an additional chamber purge or drying process, using a heated or ambient temperature cleaning fluid, such as dry N
2
CO or CO
2
gas, after the chamber has been drained. Optionally, chamber pressure is maintained near or above the external environment pressure as the rinse liquid is drained from the chamber.
In a first improvement, high velocity flow of a supplemental gas provides a controllable expansion of the selected liquid and produces a “fog” with reduced aerosol diameters and improved drying and/or cleaning action.
In a second improvement, controlled flow of a supplemental gas, combined with a mask that captures the heavier selected liquid particles (e.g., those with aerosol diameters>10 &mgr;m), produces a fog with reduced aerosol diameters and improved drying and/or cleaning action.
In a third improvement, the selected liquid is continuously circulated and filtered to continually remove substantially all contaminants with diameters greater than a selected value, such as 0.05 &mgr;m.
In a fourth improvement, a shutter is used on the delivery system for the selected liquid to suppress or substantially eliminate contaminant particle “spikes” that occur during a start-up phase of the delivery apparatus.
In a fifth improvement, an improved aerosol particle production system, using an inert particle formation surface, is provided that provides improved control of aerosol diameters and allows production of much smaller diameters.
Process parameters that can be varied to control the process include vibration frequency for creation of aerosol particles from the selected liquid, a representative aerosol particle diameter, delivery rate for the selected liquid, pressure and temperature at which the selected liquid is delivered for creation of the aerosol particles, temperature of the drying fluid used (if any), and choice of the selected liquid and of the drying fluid used (if any).
The invention requires as little as 1-2 milliliters (ml) of the selected liquid to dry objects in a chamber with volume of 10-20 liters, or smaller or larger, if desired. This approach provides several benefits. First, the process is carried out at or near room temperature, with little energy expenditure, and does not require use of heated or superheated liquids or gases for drying. Second, the process uses a very small amount of the selected liquid in a large volume of rinse liquid (10-20 liters) so that the mixture of rinse liquid and selected liquid can normally be disposed of without the special handling procedures required for hazardous materials. Third, a wide variety of inexpensive selected liquids can be used. Fourth, use of a covering film of selected liquid minimizes vapor from the rinse liquid remaining in the chamber after drainage. Fifth, the process is easily scaled up or down, with no substantial changes in the apparatus. Sixth, the process removes large diameter contaminants that are not chemically bound to an object surface.
REFERENCES:
patent: 4702418 (1987-10-01), Carter et al.
patent: 5449502 (1995-09-01), Igusa et al.
patent: 5653045 (1997-08-01), Ferrell
patent: 5685086 (1997-11-01), Ferrell
patent: 5964958 (1999-10-01), Ferrell
patent: 5968285 (1999-10-01), Ferrell et al.
patent: 6036785 (2000-03-01), Ferrell
patent: WO 97/33702 (1997-03-01), None
Carter Rob E.
Ferrell Gary W.
Spencer Thomas D.
Carrillo Sharidan
Gens Timothy H.
Schipper John
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