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A novel submount substrate with high thermal conductivity for optoelectronic devices is proposed. The substrate is fabricated by depositing an Al-based insulating film on a copper substrate. AlN films were deposited by RF reactive sputtering using an Al target (5N) in a gas mixture of Ar and N 2 . Al 2 O 3 films were deposited by oxygen-ion-assisted electron beam (EB) evaporation. Many conductive paths were detected in the AlN films.These defects were introduced in the AlN film during a photolithography process for fabricating electrode patterns because the alkaline developer dissolved the film. An Al-OH peak in Fourier transform infrared spectroscopy (FT-IR) spectra suggested that the Al(OH) 3 formation was one of the reasons for the presence of conductive paths in the AlN film. In the case of Al 2 O 3 films, no conducting path was detected in electrical measurements, and no marked change in surface morphology was observed in scanning electron microscopy (SEM) images, after treatment with the alkaline developer. The Al 2 O 3 /Cu structure is a candidate for the novel submount substrate with high thermal conductivity.

SUMMARYThe design of thin-film resistors is an important element in forming the circuits of high-precision thin-film submount substrates. In this paper, we studied the effect of the contact resistance of the electrode on the precision of a tantalum nitride (TaN x ) thin-film resistor formed by reactive sputtering. By changing the length of the resistor while maintaining a constant electrode shape, we independently evaluated the resistance of the electrode and the resistance of the resistor itself. We used the Transmission Line Model (TLM) to determine the specific contact resistivity between the TaN x thin film and the electrode and the temperature coefficient of resistance (TCR), and studied the relationship to the deposition conditions of the TaN x thin film. The resistance of the electrode had about 1/10 of the sheet resistance of the resistor and must be considered during design when fabricating a high-precision thin-film resistor. The specific contact resistivity depended on the concentration of nitrogen in the TaN x thin film and was on the order of 10 -8 Ωm 2.