Effect of negative bias voltage on the microstructures of AlN thin films fabricated by reactive r.f. magnetron sputtering

Abstract

Aluminium nitride thin films have been fabricated on silicon wafers by reactive r.f. magnetron sputtering in mixed Ar-N2 discharge with variation of negative bias voltage. The effect of negative bias voltage on the microstructures of AlN thin films have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), stress measurement, Auger electron spectroscopy (AES), etc. While the negative bias voltage was varied in the range 0 to −45 V, highly c-axis oriented film can be fabricated at −30 V, and the grain size and compressive stress increase with the negative bias voltage. From the plasma analysis, the dominant positive chemical species is identified as N+2 ions. The above results can be understood considering that at the kinetic energy transfer and flux of N+2 ions increase with increasing negative bias voltage.