Structural modifications of sintered aluminum nitride ceramics resulting from excimer laser irradiation

Due to their unique physical properties (high thermal conductivity, high electrical resistivity) aluminum nitride (AlN) ceramics are attractive materials for applications in electronics and other medium or high power electrical networking. In this contribution, the change of surface configuration of sintered AlN plates is studied as a function of excimer laser irradiation conditions (fluence, number of pulses). Before irradiation, Auger Electron Spectroscopy reveals a surface composition which is characteristic of the AlN synthesis process, i.e. N, O and C atoms are present, without any evidence for Al. At high laser fluences, irreversible decomposition of AlN takes place, producing free Al atoms at the surface. At low fluence, long-term and reversible modifications are detected, leading to the formation of metastable nitrogen oxides. The kinetics of these laser-induced reversible modifications is analyzed and a model is proposed to support these experimental evidences and to explain the AlN permanent decomposition.