Excimer laser direct write aluminum on aluminum nitride

Fabrication of metal lines on aluminum nitride (AlN) ceramic is important for application of AlN as a microcircuit board. An Al line can be made directly from AlN by excimer laser exposure. All lines in this paper were written by pulsed KrF excimer laser (248 nm) in air and vacuum at different scan speeds with a constant laser energy. The morphology of the Al lines was observed by optical and scanning electron microscopies. The lines become more metallic when the scan speed decreases. Consequently the resistance, measured by the four-point probe technique, decreased to a minimum value in the scan speed range of 400 μm/s to 900 μm/s for the samples made in air. The resistance of Al lines written in air is greater than that in vacuum because of oxidation. The samples made in air with scan speed lower than 400 μm/s were heavily oxidized. SAXPS spectra showed a strong oxidation state and that the excimer laser exposure depletes nitrogen from AlN. The Al lines produced by laser-induced decomposition of AlN board are being evaluated as catalysts for laser assisted CVD and conventional electroless plating. The oxidation layer on the surface of Al lines may effect the adhesion between the Al lines and the deposited or plated metal.