A study on the high rate deposition of CrNx films with controlled microstructure by magnetron sputtering

High rate deposition of CrNx films with control of microstructure was carried out by magnetron sputtering. For these purposes, the deposition processes parameters were varied: N2 flow rate and especially substrate bias voltage, duty cycle and frequency using a pulsed DC power supply. The microstructure was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and mechanical properties were evaluated by a microhardness test and adhesion test. The maximum deposition rate for CrNx compound films could be reached to nearly 90% compared with that for pure Cr coating due to the increase of ionization efficiency caused by a negative-pulsed DC bias. As N2 flow rate is increased, the microstructure of CrNx films was changed from Cr+Cr2N to CrN. Also, a phase transformation occurred between Cr2N+CrN multi-phase and CrN mono-phase by control of a negative DC and/or pulsed DC bias voltage, duty cycle and frequency. Microhardness for CrNx films were measured to be up to 1600 kg/mm2 and the maximum hardness value of 2250 kg/mm2 was obtained for CrNx film deposited with a N2 flow rate of 20 sccm at a negative DC bias of −100 V.