Characterization of the photoresist residue in integrated thermionic devices

Abstract

A study of the thermal decomposition of the Kodak thin-film resist (KTFR) used in the fabrication of integrated thermionic emission devices is presented. In contrast to conventional cathode fabrication schemes which typically employ a nitrocellulose binder, the use of KTFR is shown to produce a carbon residue which persists even at cathode operating temperatures. The degree of residue formation is dependent on the heating rate. Differential thermal analysis and thermal gravimetric analysis studies indicate that the deomposition of the resist occurs at about 450 °C. The presence of the residue is shown to influence the breakdown of the cathode carbonate mixture. X-ray photoelectron spectroscopy analysis of the residue reveals that it is either graphitic- or hydrocarbon-like in nature. In contrast to conventional binders the KTFR residue is not oxidized by CO2 at temperatures below 650 °C. At higher temperatures the time courses of the residue concentration were measured and indicated the presence of residual signal even after the decay appeared complete. The ramifications of the presence of a carbon residue at cathode operating temperatures are discussed.