Atomic layer deposition of AlN from AlCl3 using NH3 and Ar/NH3 plasma

Abstract

The atomic layer deposition (ALD) of AlN from AlCl3 was investigated using a thermal process with NH3 and a plasma-enhanced (PE)ALD process with Ar/NH3 plasma. The growth was limited in the thermal process by the low reactivity of NH3, and impractically long pulses were required to reach saturation. Despite the plasma activation, the growth per cycle in the PEALD process was lower than that in the thermal process (0.4 Å vs 0.7 Å). However, the plasma process resulted in a lower concentration of impurities in the films compared to the thermal process. Both the thermal and plasma processes yielded crystalline films; however, the degree of crystallinity was higher in the plasma process. The films had a preferential orientation of the hexagonal AlN [002] direction normal to the silicon (100) wafer surface. With the plasma process, film stress control was possible and tensile, compressive, or zero stress films were obtained by simply adjusting the plasma time.