Aluminum nitride (AlN) is gaining increasing interest as an attractive substrate material for electronic applications in high power density packing owing to such features as: high thermal conductivity, good electrical insulation, thermal expansion similar to silicon and non-toxicity. The requirement of heat dissipation imposes the need of forming low thermal resistance (thin) joint with a high thermal conductivity metal, preferably copper. According to recent literature the direct bonding (DB) of the substrate to the conductor is considered as the most promising technique.
Recently satisfactory result of AlN-Cu bonding was demonstrated by addition of 1-1.5 at % of oxygen as an active element to AlN-Cu system without intentional modifying of the substrate surface.
In our approach it is expected that formation of nano-size interface layer with enhanced content of favorable additives introduced by ion implantation into AlN and pre-oxidation of Cu should result in even better wettability between the bonded elements.
For ion implantation into commercially available AlN substrates Ti, Fe and O ions have been chosen. The choice of Ti was dictated by a commonly known beneficial effect of this element on metal-ceramic joints quality. There is also some evidence that similar behavior can be expected of iron. Oxygen implantation is considered as a low temperature alternative to thermal oxidation of AlN surface - known to improve adhesion of copper layer.
The implantation was carried out with the doses of 5x10¹⁵ cm^-2, 2.5x10¹⁶ cm^-2, 1x10¹⁷ cm^-2 at ion energy of about 140 keV. Cu foils were oxidized in air at 380^oC for 10 min. DB process was performed at 1085^oC in flowing nitrogen. The best results of shear strength, sufficient for electronic applications, were obtained for Ti implanted and additionally post-implantation oxidized substrates. The results are discussed in terms of possible compositional phases formed during the technological process.

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