Hydrogen-free amorphous silicon nitride (SiNx) films were deposited at room temperature by microwave electron cyclotron resonance plasma-enhanced unbalance magnetron sputtering. Varying the N-2 flow rate, SiNx films with different properties were obtained. Characterization by Fourier-transform infrared spectrometry revealed the presence of Si-N and Si-O bonds in the films. Growth rates from 1.0 to 4.8 nm/min were determined by surface profiler. Optical emission spectroscopy showed the N element in plasma mainly existed as N+ species and N-2(+) species with 2 and 20 sccm N-2 flow rate, respectively. With these results, the chemical composition and the mechanical properties of SiNx films strongly depended on the state of N element in plasma, which in turn was controlled by N-2 flow rate. Finally, the film deposited with 2 sccm N-2 flow rate showed no visible marks after immersed in etchant [6.7% Ce(NH4)(2)(NO3)(6) and 93.3% H2O by weight] for 22 h and wear test for 20 min, respectively. (C) 2009 Elsevier B.V. All rights reserved.