Improvement in crystal orientation of AlN thin films prepared on Mo electrodes using AlN interlayers

Highly c-axis oriented aluminum nitride (AlN) thin films have been prepared on molybdenum (Mo) bottom electrodes using AlN interlayers (AlN-IL), by reactive rf magnetron sputtering. The interlayers were deposited between the Mo electrodes and silicon substrates, such as AlN/Mo/AlN-IL/Si. The crystallinity and crystal orientation of the interlayers depend on the interlayer thickness and strongly influence those of the Mo electrodes and AlN films. From transmission electron microscopy observations and X-ray pole figure measurements, the interlayer, Mo electrode and AlN film consist of columnar grains and exhibit a fiber texture. It has been found that they have the local epitaxial relationship of image. The nucleation process of AlN thin films changes from a fine grain structure to a columnar structure.