The c axis oriented AlN films on Si (100) substrates diameter of 6.35 cm are prepared using N 2, Ar and AlCl 3 vapour via electron cyclotron resonance plasma enhanced chemical vapor deposition. The characterization of film is investigated by means of X ray diffraction (XRD), energy dispersive X ray analysis and scanning electron morphology. The dependences of the c axis orientation of the AlN film on the microwave power, substrate temperature and N 2 flow rate are studied. High quality AlN films of large area and c axis standard deviation less than 5° are obtained.