Preparation And Surfacial Metallization Of Aluminum Nitride Thin Films

High density package is gradually being the mainstream of the technologydevelopment as large scale integrated circuit is developing towards the trend of highdensity, high-speed, multi-function and small size. However, high density of thedevices would result in the increasing of heat production per function unit, whichinduce the operating temperature increase greatly if the heat dissipation efficiencyhas no obvious improvement. The substrates with low dielectric constant, lowthermal expansion coefficient and high thermal conductivity must be used to pretectthe circuit components from the damage induced by heat accumulation and thermalcycling.Aluminum nitride (AlN), with high thermal conductivity, non-toxic, lowdensity and matching thermal expansion with silicon, has become an ideal materialfor IC packaging. The surface of AlN needs to be metalized for its application incircuit layout. The growth optimization of AlN thin films and the process ofmetallization on AlN thin films were studied in this paper.The AlN thin film had been grown by reactive magnetron sputtering. It showsthe optimal condition for AlN growth,0.6Pa for working pressure,1:4forargon/nitrogen ratio and300W for sputtering power.By the pretreatment on the surface of substrate, it will contribute to the growthof AlN seed crystal. The scratch quantity will be more with longer polishing time.The acid treatment of deposited AlN thin film reduced the particles of aluminum toimprove the quality of AlN surface.Titanium (Ti) thin film had been deposited on the AlN films by DC magnetronsputtering and annealed under certain conditions. Copper (Cu) thin film had beendeposited on the AlN-Ti sample by DC magnetron sputtering and annealed undercertain conditions. From the cross sectional view of the sample, there were threelayers sequentially grown on the substrate. The binding forces between the films hadbeen tested with nano-indentation. The optimal condition of metallization was set at the temperature of500℃and the time of30min by annealing.The critical load ofAlN-Cu was only400μN, while the critical load of AlN-Ti-Cu was850μN, whichachieved a better result on the metallization by introducing the Ti layer.