Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-11-12
2001-04-03
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S307700, C134S184000, C134S902000
Reexamination Certificate
active
06210510
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to polymer protection for an energy source or sensor in a chemical bath. More particularly, the invention relates to a structure that provides a high level of protection and a high level of energy transmission. More particularly, the invention relates to an ultrasonic system having improved energy transfer without leakage.
BACKGROUND OF THE INVENTION
Sonic energy is used in semiconductor fabrication to enhance wet chemical processing. The efficient transfer of energy between energy source and liquid chemical bath is limited, however, where the transducer must be protected from aggressive chemicals. Significant energy losses occur at interfaces, particularly where there is an air gap.
Some prior art systems have had a sonic transducer bonded to a metallic plate which in turn is mounted to an outside wall of a chemically inert polymeric vessel. The transducer can be bonded firmly to the metal plate and the plate provides means for removing heat from the transducer, improving its reliability. But this structure has not been adequate to provide efficient delivery of sonic energy to the chemical bath where it is desired to form vessel walls from a flourocarbon polymer, such as teflon, for which there is no good adhesive between metal plate and polymer wall. The inability to provide intimate bonding at this interface has limited the use of such polymers for tank walls.
To counter this problem, other systems have sealed sonic transducers in a polymeric protective coating and placed them inside the processing vessel. However, this solution exposed the polymer coating, transducers and their electrical connections to the sometimes corrosive properties of the processing liquid. Polymer coating or seal failures have sometimes led to the contamination of semiconductor wafers in the chemical bath or to failure of the transducers or their mountings.
Because the thermal expansion coefficient of polymers is usually much larger than that of the transducers and substrates, where there is heating of the transducer or substrate, differential thermal expansion increases the gap between transducer or substrate and the coating, reducing the efficiency of energy transfer. This in turn increases the local temperature, exacerbating the problem and lowering transducer reliability. The thermal expansion not only degrades coupling of energy between transducer and processing fluid, it also can cause stress cracks and leaks through the polymer.
The air gap problem is best illustrated for an immersion heater type transducer that has a polymer coating. If an air gap develops between heater and coating the flow of heat out of the heater will be reduced, and so the temperature of the heater will increase. Portions of the polymer coating still contacting the heater will also get hotter. Since the polymer coating typically has a much larger thermal expansion coefficient than the heater, the polymer coating is likely to further expand away from the heater. In this case the heater will continue to increase in temperature, and ultimately the polymer will melt at the few points of contact.
A better solution is needed that provides a high level of coupling between transducers and their polymeric protective coats and a high level of transmission through the protective coats to the processing liquid chemical bath without introducing the risk of seal failures, and this solution is provided by the following invention.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a structure that facilitates intimate contact between a low adhesive polymer, such as a fluoropolymer or a polyolefin, and a substrate.
It is a further object of the present invention to provide intimate contact between a a low adhesive polymer and a substrate as temperature vanes.
It is a further object of the present invention to provide intimate contact between a polymer and a substrate holding a component, such as a transducer, for efficiently transferring energy therebetween.
It is a further object of the present invention to provide efficient coated sonic transducers without gaps, seams, or seals for a chemical process vessel.
It is a feature of the present invention that differential thermal expansion is used to provide improved mechanical contact between a polymer coating and a substrate, providing a high level of mechanical coupling to low adhesion polymers, while retaining sufficient coupling as process temperature increases.
It is an advantage of the present invention that energy transfer efficiency and reliability is improved and system operating cost is reduced compared to present systems.
These and other objects, features, and advantages of the invention are accomplished by an apparatus for use in an external environment. The apparatus comprises a substrate having a convex surface having a component connected thereto. A layer of polymer extends across at least a portion of the convex surface. The polymer is under a tensile stress. The polymer is in physical contact with most of the portion of the convex surface as a result of the stress. The polymer seals the substrate from the external environment.
In one embodiment, the film of polymer stretched over the convex substrate is the wall of a chamber, the component is mounted on a side of the substrate opposite the convex surface, and the stretching of the polymer over the substrate is accomplished by differential thermal contraction during a cooling of the wall and substrate.
REFERENCES:
patent: 5383484 (1995-01-01), Thomas et al.
Kern, Jr. Frederick William
Martin Donald Joseph
International Business Machines - Corporation
Walsh Robert A.
Yao Sam Chuan
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