Growth of Hf(C,N) thin films on Si(100) and D2 steel substrates by plasma assisted MOCVD

We have deposited Hf(C,N) thin films on Si(100) and STD11 steel substrates by pulsed d.c. plasma assisted metal–organic chemical vapor deposition (PA-MOCVD) in the temperature range of 200–300°C. Tetrakis diethylamido hafnium, Hf[N(CH2CH3)2]4 (TDEAH), was used as the hafnium precursor. A mixture of He (90%) and H2 (10%) in volume ratio was used as the carrier gas, and the N2 was used as the reactive gas. During CVD, radical formation and ionization behaviors in plasma were analyzed in situ by optical emission spectroscopy (OES) at various pulsed bias voltages and N2 flow rates. The deposition rate with the change of the flow rate ratio of N2 reactive gas to He+H2 carrier gas was also increased to 0.1. With increasing bias voltage, moreover, the film growth rate was continuously increased resulting in carbon-rich films. Highly oriented oxygen-free, polycrystalline Hf(C,N) thin films in the {111} direction were successfully grown on the STD11 steel substrate at 300°C. The hardness of film changed from 1000 to 2500 HK, depending on N2 gas flow rate ratio and bias voltage. Higher hardness can be obtained for a N2 gas flow rate ratio of 0.1 and bias voltage of 600 V. The film composition was confirmed with XPS and RBS analysis, and the N2 reactive gas makes low carbon contents in the films. SEM revealed that surfaces of as-deposited Hf(C,N) thin films were smooth and featureless.