PECVD RF versus dual frequency: an investigation of plasma influence on metal–organic precursors' decomposition and material characteristics

Plasma enhanced metal organic chemical vapor deposition (PEMOVCD) of titanium nitride with dual frequency plasma sources were studied by means of plasma and material characterization. Adding a low frequency to a radio frequency plasma in order to enhance the deposition reaction mechanism is demonstrated. An in depth investigation of plasma by optical emission spectroscopy shows that due to secondary electrons heating the plasma, it enters a gamma-mode and that LF permits better dissociation of the H2 reactant gas. Moreover, it appears that the TiN metal organic precursor is not completely dissociated (no Ti* emission) but new species are observed that indicate a different fragmentation of the precursor. When LF plasma is used these modifications can be correlated to a change in the deposition reaction mechanism which affects the properties of the deposited material. Strong modifications of the TiN properties and deposition rate are observed when adding 17–60 W LF to a 200 W RF plasma. For example, with 35 W LF added to a 200 W RF, the deposition rate is increased by a factor two and the film appears to be less resistive (by 50%) and has a higher density. Such effects are not observed when only increasing the RF power (from 200 to 300 W with no LF power). (paper)