Electrical and structural properties of conductive nitride films grown by plasma enhanced atomic layer deposition with significant ion bombardment effect

Abstract

Conductive metal nitrides are widely used in the microelectronics industry as interconnects, thin film resistors, electrodes, and diffusion barriers. These films are commonly prepared by sputtering and chemical vapor deposition, which are suitable for planar geometries. However, conformal deposition onto 3D and complex structures requires the use of atomic layer deposition (ALD). In this work, we compare the electrical and structural properties of various metallic nitrides (namely, TiNx, ZrNx, HfNx, and TaNx) prepared by ALD from metalorganic precursor and H2/Ar plasma. Despite similar bulk resistivity values of these films, we find significant differences in their measured resistivity for the thin film (by ALD). TiNx and ZrNx show metallic behavior with a positive temperature coefficient of resistance (TCR), whereas HfNx and TaNx show semiconducting behavior with negative TCR values. Microstructure and film chemistry of deposited films are investigated by x-ray photoelectron spectroscopy and transmission electron microscopy, and the correlation between the electrical and structural parameters of the deposited films is discussed. It is shown that a high concentration of carbon contamination is related to smaller grain size and higher electrical resistivity. TiNx exhibits the lowest carbon contamination, largest degree of crystallinity and lowest resistivity (∼60 μω cm) highlighting its potential as ALD-grown metal. Other nitrides and their combinations can be used to tailor specific resistivity and TCR values for thin film resistor applications in 3D and complex geometries such as deep trenches. Overall, this study provides useful guidelines toward the development of ALD nitrides for use in the microelectronics industry.