Metallization and photolithographic processes and procedures for MC2730 RTG thermopile intraconnections

Abstract

Processes and procedures have been developed for applying the thin film tungsten electrical intraconnections to the MC2730 RTG "one-dimensional" thermopile after polishing, the surface to be metallized is cleaned with a detergent/organic solvent procedure and then etched with hydrofluoric acid to minimize the oxide. Tungsten contacts are sputtered onto the thermopile and the individual contacts are photolithographically defined using a negative acting photoresist in conjunction with a potassium ferricyanide etchant. The processes detailed in this report were used to process 89 thermopiles with an 80% effective yield. 0 DISTRIBUTION OF W»^*

Effect of heat treatment on the electrical resistance of photoresist as related to radioisotopic thermoelectric generator aging

“…The aging behavior of a generator was simulated using a unit prepared under carefully controlled, thought to be "ideal," conditions (9). The photoresist was not removed after the photolithographic process (2). This left photoresist on the tungsten electrodes and on the sides of the thermopile, bridging the thermopile channels over a distance It is also certainly possible that the photoresist may not be the cause of the generator aging problem.…”

“…Tungsten electrodes were sputtered on to the glass surface and were '^2 cm in length and were spaced '^^1 cm apart. Photoresist was applied using standard spinning techniques (2). Thicknesses were estimated to be '^•1 um.…”