Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal
Reexamination Certificate
2000-12-22
2001-10-23
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
C438S745000
Reexamination Certificate
active
06307240
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the use of a pulsed flow of chemical etchant in chemical etching manufacturing systems to remove material from a workpiece, and to a method for use thereof.
There are a wide variety of conventional chemical etching manufacturing systems using a continuous flow of etchant to remove material from a workpiece including spray etching, immersion etching, and bubble etching. The use of a uniform flow of etchant in each of these conventional chemical etching manufacturing systems is subject to certain limitations and disadvantages.
In spray etching systems, a workpiece is horizontally or vertically positioned in a box-like chamber with spray nozzles directing a uniform flow of etchant against the workpiece. The spray nozzles are oriented to enhance coverage of etchant on the workpiece as well as to introduce fresh etchant to the workpiece coverage area. The use of a uniform flow of etchant on a horizontally or vertically positioned workpiece generally results in non-uniform etching with different areas of the workpiece receiving varying amounts of etchant, especially at the edges of the workpiece.
In immersion etching systems, a workpiece is immersed in chemical etchant until the etching is complete. Process times are generally long and known heating and mechanical agitation methods tend to lead to non-uniform etching.
Bubble etching is a modified form of immersion etching, using air bubbled through the chemical etching solution past the workpiece being etched. The bubbling of air assists in removing material and providing fresh etchant at the etched surface. However, it is often difficult to obtain a uniform distribution of bubbles throughout the workpiece and therefore difficult to obtain uniform etching.
In all of these chemical etching manufacturing systems, the use of an uniform flow of etchant on a workpiece may lead to problems with non-uniform etching and to overall difficulties with the precision of the etching.
BRIEF SUMMARY OF THE INVENTION
It is in general an object of the invention to provide more uniform etching through the use of a pulsed flow of chemical etchant in chemical etching manufacturing systems. Improvement may also be obtained in the etch rate and etch quality, such as the undercut on the etched workpiece.
In a preferred embodiment, the chemical etching manufacturing system includes a fluid control device, a fluid injection device, and a pulsed flow of chemical etchant. At least one of fluid flow and fluid pressure is controlled by the fluid control device. The pulsed flow of chemical etchant is adapted to pulsedly contact and remove material from a workpiece. Control over the pulse of the pulsed flow of chemical etchant is regulated by the fluid control device. The pulsed flow of chemical etchant is emitted from the fluid injection device.
In another aspect, a method of chemical etching in a manufacturing system is detailed. Initially, a workpiece is provided. Next, the workpiece is introduced to a pulsed flow of chemical etchant. The flow of chemical etchant pulsedly contacts and removes material from the workpiece. Finally, the workpiece is removed from the pulsed flow of chemical etchant.
In yet another aspect, another method of chemical etching in a manufacturing system is detailed. Initially, a workpiece, a fluid control device, and a fluid injection device are provided. The fluid control device controls at least one of fluid flow and fluid pressure. Next, the workpiece is introduced to a pulsed flow of chemical etchant. The flow of chemical etchant pulsedly contacts and removes material from the workpiece. Control over the pulse of the pulsed flow of chemical etchant is regulated by the fluid control device, and the pulsed flow of chemical etchant is emitted from the fluid injection device. Finally, the workpiece is removed from the pulsed flow of chemical etchant.
The present invention provides significant advantages over other uniform flow chemical etchant methods and systems. In particular, the method and system of the present invention more thoroughly breaks up the surface to be etched in workpieces, enhances mixing of etchant, provides improved flow of fresh etchant on the surface to be etched, and promotes uniformity of etching by making the etching process less sensitive to flow at the edges of the surface to be etched.
The present invention, together with further objects and advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.
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Achari Achyuta
Goenka Lakhi N.
Brinks Hofer Gilson & Lione
Hoang Quoc
Nelms David
Visteon Global Technologies Inc.
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