Electron-Enhanced Atomic Layer Deposition of Tunable TiC x N y Ternary Nitride Films Using Tetrakis(dimethylamido)titanium with Ammonia Reactive Background Gas

Electron-enhanced atomic layer deposition (EE-ALD) of amorphous, tunable titanium carbonitride (TiCxNy) films was obtained at low temperatures. The TiCxNy EE-ALD was achieved using sequential exposures of tetrakis(dimethylamido)titanium (TDMAT) and low-energy electrons in the presence of a continuous NH3 reactive background gas (RBG). The composition of the TiCxNy films was tuned by varying the NH3 background pressure and the electron exposure time. The TiCxNy EE-ALD was performed by utilizing a hollow cathode plasma electron source (HC-PES). The HC-PES delivered a high electron flux into background gases at pressures up to several mTorr. TDMAT was used as the source of Ti, C, and N. The NH3 RBG served as both a source of additional N and a method for the removal of C from the TiCxNy films. The TiCxNy EE-ALD film growth was monitored using in situ ellipsometry. The TiCxNy EE-ALD was conducted at low temperatures that never exceeded 130 °C, using NH3 pressures from 0 to 3 mTorr. The C content in the TiCxNy films could be tuned using the NH3 RBG pressure. Lower NH3 pressures led to the incorporation of more C into the TiCxNy films. The C:Ti ratio varied from ∼0.3 to ∼0.05 versus NH3 RBG pressure, as measured by X-ray photoelectron spectroscopy (XPS), at a constant electron exposure time of 10 s. Electron exposure time was also used to modulate the C content in the TiCxNy films. Shorter electron exposures led to more C incorporation. The C:Ti ratio varied from ∼2 to ∼0.1 versus electron exposure time, as measured by XPS at a constant NH3 background pressure of 2 mTorr. In situ 4-wavelength and ex situ spectroscopic ellipsometry were able to estimate electrical resistivities for the TiCxNy films. Resistivity was reduced from >2000 μΩ cm to ∼200 μΩ cm with decreasing C content. X-ray reflectivity (XRR) measurements were able to determine film densities. The film density for TiN films was 4.6 g/cm3, and the film density decreased with increasing C content. The C content in the TiCxNy films could also be varied using a CH4 RBG. Carbon could be added by carbon EE-chemical vapor deposition (EE-CVD) using electron exposures together with a CH4 RBG. The carbon could also be removed by carbon EE-chemical vapor etching (EE-CVE) using electron exposures together with NH3 RBG. The C content in the TiCxNy films was difficult to control using a supercycle approach with TiN EE-ALD and carbon EE-CVD.