Control of Crystallographic Structure of Aluminum Nitride Films Prepared by Magnetron Sputtering

Aluminum nitride (AlN) films were prepared by using reactive magnetron (RMS). The substrate temperature (T_s) was varied from room temperature to 700°C, and RF power (P _w) from 100 to 250 W, and three different substrate materials (e.g. Si(100), Pt(111)/Si(100) and Al₂O₃(00·1)) were used. The mean free path of the species in the vacuum was controlled to be much shorter than the target-to-substrate distance, so that T_s and P _w have the equivalent effect in affecting the effective thermal energy of the species after landing on the substrate. With these conditions, the film structure was found to cover a broad range, varying from nearly amorphous (na-), polycrystalline (p-), (00·1) texture (t-) and epitaxial (e-) structure. The structural change is supposed to be governed the successive increase in the thermal energy of the species on the substrate. The use of substrate material having lattice matching with the AlN structure further assists the (00·1) preferential growth when the species are mobile enough at the settings of high T_s and P _w.