1. Field of the Invention
The present invention relates to lithography, and more specifically, it relates to techniques for transferring parallel and evenly spaced patterns of light into conductive rings in or on the walls of a cylinder for use as a high gradient insulator.
2. Description of Related Art
Provisional Patent Application Ser. No. 60/039,979, filed Mar. 4, 1997 and titled "High Gradient Insulator," incorporated herein by reference, describes an approach for inhibiting the flashover breakdown of insulator structures by using alternating planes of insulator and conductor. One means of producing high gradient insulator designs includes stacking thin insulating cylinders and fusing them into one large cylinder with conductive material at the interface in between. That stack is subsequently machined to the desired geometry. This is a difficult and expensive process.
A high gradient insulator can also be achieved by simply embedding conducting rings into the surface of the insulator. One method involves selective removal of Chrome (coated on the insulator) using a laser (or other tool) while being rotated on a lathe to create a mask which is used for etching. This is also difficult and expensive to do properly.
The easier method of generating surface embedded conductors (narrowly spaced metal rings concentric with the cylinder) involves using lithographic techniques. Lithography is defined here as a method whereby light converts photoresist (or simply resist) into a mask by proper exposure of the resist and subsequent processing (including development). Developing resist entails use of a liquid developer to dissolve regions of resist where light either existed or did not exist during exposure. The effect of developer on exposed or unexposed resist depends on prior processing and whether positive or negative resist is used.
Three major problems are addressed by the lithographic technique. The need for fusing thin insulators together is eliminated. The need for using a lathe, where it is time consuming and difficult to align the cylinder axis to perfectly coincide with the axis of the lathe, is eliminated. An optical pattern is easily generated to properly expose the resist all at once. Eliminating moving parts simplifies the task enormously. Finally, the lithographic technique is able to reduce the spacing between conductors (say down to 300 nm). Interference lithography is the only fabrication method that can work on this scale. Just how fine the spacing can be and still get an increased benefit is still under investigation.