Metallization of AlN

Heat dissipation from silicon chips is becoming critical as a result of increasing circuit density and power applied to these chips. In this regard, aluminum nitride (AlN) is the most promising candidate to be used as a substrate since it possesses high a thermal conductivity and thermal expansion coefficient close to that of silicon. In addition, metal-ceramic interfaces determine the heat dissipation through a circuit. In order to minimize the effect of interfaces, direct bonding (DB) of AlN to Cu was studied. DB process has been reported to provide a low thermal barrier and an interface which is free of thermal fatigue.In this work process parameters of DB were optimized based on time, temperature and thickness of the Cu-foil for Cu-Al$ sb2$O$ sb3$ system in a N$ sb2$ atmosphere containing 500 ppm O$ sb2$ in a temperature range of 1065 to 1075$ sp circ$C. These conditions were then applied to the Cu-AlN system. Wettability of AlN by Cu was studied and improved through oxidation of AlN and modification of Cu by adding 1 at.% O$ sb2$. The activation energy for oxidation of AlN was found to be 94 kJ/mol. It was then shown that direct bonding of Cu to AlN can be performed without any intermediate layer. The average peel strength of AlN-Cu, A$ sb2$O$ sb3$-Cu and AlN-Al$ sb2$O$ sb3$-Cu systems were measured to be 42, 49 and 14.7 MPa, respectively