Accelerating the oxidation rate of AlN substrate through the addition of water vapor

To apply a pre-oxidation treatment on aluminum nitride (AlN) substrate is a common practice before its metallization. In the present study, the microstructure of AlN after oxidation either in dry air or in wet air is characterized. The resulting thermal conductivity is measured. With or without the presence of water vapor, the oxidation of AlN is a reaction-dominating process. The addition of water vapor speeds up the oxidation rate by one order of magnitude. The surface oxide layer is full of nano-sized pores. The presence of surface oxide reduces the thermal conductivity by ∼15% when the thickness of oxide layer is only 3 μm.