Study on plasma assisted metal-organic chemical vapor deposition of Zr(C,N) and Ti(C,N) thin films and in situ plasma diagnostics with optical emission spectroscopy

Abstract

Zr(C,N) and Ti(C,N) films were synthesized by pulsed dc plasma assisted metal-organic chemical vapor deposition method using metal-organic compounds of tetrakis diethylamido titanium and tetrakis diethylamido zirconium at 200–300°C. To change the plasma characteristics, different carrier gases such as H2 and He∕H2 were used and, as the reactive gas, N2 and NH3 were added to the gas mixture. The effect of N2 and NH3 gases was also evaluated in the reduction of C content of the films. Radical formation and ionization behaviors in plasma were analyzed by optical emission spectroscopy and mass spectrometry at various pulsed biases and gas conditions. The gas mixture of He and H2 as the carrier gas was very effective in enhancing the dissociation of molecular gases. In the case of N2 addition, N2 as reactive gas resulted in higher hardness. However, NH3 as reactive gas highly reduced the formation of CN radical, thereby greatly decreasing the C content of Zr(C,N) and Ti(C,N) films. The hardness of the film is 1400–1700HK depending on gas species and bias voltage. Higher hardness can be obtained for a H2 and N2 gas atmosphere and bias voltage of −600V. Plasma surface cleaning using N2 gas prior to deposition appeared to increase the adhesion of films on steel. The changes of plasmas including radicals and film properties are illustrated in terms of carrier and reactive gases, as well as pulsed power variation.