Self-Aligned Cathode Deposition Process for Planar Cathode-Grid Structures
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
A self-aligned cathode deposition process for planar cathode-grid structures is described. This process permits the placement of a heater on the frontside of a substrate and thus leaving the backside free of metal and transparent, thereby allowing accurate cathode alignment and avoiding self-biasing effects. A planar cathode-grid for integrated vacuum tubes consists of a thin metal film evaporated onto an insulating substrate. This film is then etched into cathode and grid structures. Thin oxide cathodes are patterned photolithographically onto the cathode pads. Vital to the design is the need for accurate cathode alignment in order to get accurate control voltages, and avoid self-biasing effects due to uncoated parts of the cathode pad.