Abstract
Commercially available tape-case AIN substrates of > 99.5-percent purity were used in this study. Also, 99.5-percent pure alumina substrates were used as control samples. These substrates were tested for stability in water and in air, for laser scribability, and for thin film adhesion and pattern generation. In water, an AIN surface decomposes to a porous surface film of a hydrated alumina phase at 100°C. This decomposition film adversely affects the adhesion of thin films. In air, AIN oxidizes to a-alumina when heated above 1OOO”C. No obvious surface decomposition of AIN was observed in SEM micrographs of the samples aged at 8S4C/85-percent humidity for lo00 h. AIN is laser scribable and, unlike A1203, it does not undergo a phase transformation in the scribed region. Thin films of Ti, Pd, and Au with and without Ta,N were sequentially sputter-deposited on AIN. Adhesion of these films was adequate as confirmedl by a soldered lead pull test. Next, triple-track resistor pattern containing 300 A thick Ta2N resistors with 76-pm width, and spaced 76 pm apart with Ta2N, Ti, Pd, and Au contact pads were developed by photolithography. The adhesion of patterned thin film of sequentially deposited Ti, Pd, Au, and TazN on AIN substrates was good even after aging them for lo00 h at 8S0C/85-percent humidity. However, 53 percent of the thlin-film resistors on AIN had electrical “opens,” whereas no “opens” were observed on alumina substrates. This is attributed to poorer fine-line definition on AIN caused by its high surface roughness. The surface roughness of AIN substrates was fourfold higher than that of the alumina used in this study.
Published Version
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