Electrical and structural characteristics of sputtered c-oriented AlN thin films on Si (100) and Si (110) substrates

This paper discussed about the morphological and electrical properties of c-axis oriented aluminium nitride (AlN) thin films grown on Si (100) and Si (110) substrates by direct current (DC) reactive sputtering technique. Both the films showed intense (002) peak with the texture coefficient (γ) of 3.1 and 2.8 corresponding to Si (100) and (110) substrates. The AlN/Si (110) have grain sizes (20–30 nm) compared to the relatively denser grains (30–40 nm) of the film on Si (100) substrate. Both the films exhibited slanted columnar structures with slanting angle of 15° (Si (100) substrate) and 20° (Si (110) substrate). The dielectric constant values of the films at low frequency are found to be 7.4 and 8.8 corresponding to the Si (100) and Si (110) substrates respectively. The variation in dielectric constant values over the low frequency regime seems to be due to the presence of trapped charges present in the AlN layer and AlN‑silicon interface (interface trap density~1012 cm-2 eV−1). The flat band voltages are found to be 0.85 V and − 0.35 V corresponding to the Si (100) and (110) substrates respectively. The AlN/Si (100) film showed poor leakage current density ~ 10−4 A/cm−2 as compared to AlN/Si (110) (~ 10−5 A/cm−2). The AlN films exhibited dielectric breakdown field of 4.4 MV/cm and 6.6 MV/cm corresponding to the Si (100) and Si (110) substrates respectively.