Atomic Layer Deposition of Titanium Nitride Thin Film by Ultra Low Electron Temperature Plasma

Abstract

The diffusion barrier can be classified as a transition metal (Ti, Ta, W etc.), a transition metal nitride, or a multi component barrier such as ZrTiNi, NiCoP. Among them, titanium nitiride (TiN) has advantages including a high melting point, low resistivity, excellent thermal/chemical stability, and high corrosion/diffusion resistance. Also, titanium nitride thin film has high imperviousness and good adhesion with SiO2. TiN thin film has usually been deposited using physical vapor deposition (PVD) or chemical vapor deposition (CVD). TiN thin films deposited by PVD has properties of low concentration of impurities, rapid deposition rate and low deposition temperature, but also poor step coverage [8, 9]. TiN thin films deposited by CVD have uniformity of thin film [10]. However, the CVD requires quite high deposition temperature compared to PVD.

To overcome the disadvantage of PVD and CVD, TiN thin films has usually been deposited using atomic layer deposition (ALD). ALD offers low concentration of impurities and requires low deposition temperature. Furthermore, ALD provides excellent step coverage on high aspect ratio structures. In addition, there is plasma enhanced atomic layer deposition (PEALD) which offers higher thin film growth rate and much lower deposition temperature as compared to thermal ALD due to its highly reactive plasma radicals that reacts with precursor actively. Also, flatness as well as atomic cleanliness on the surface of the substrate is required when manufacturing ultra-thin integrated devices, but the PEALD process has its own disadvantage such as ion bombardment which causes damage to the thin films.

To reduce the damage of ion bomabardment, deposition of titanium nitride (TiN) thin film has been studied by ultra low electron plasma enhanced atomic layer deposition (ULET PEALD) using TDMAT(C8H24N4Ti) precursor and argon/nitrogen plasma. The atomic force microscopy (AFM) measurements determined a surface roughness of TiN film deposited by UELT PEALD approximately 0.3 nm. The x-ray diffraction (XRD) analysis showed crystallinity of TiN (111) and TiN (200). Also, the resistivity of TiN film deposited by ULET was approximately 325 – 365 μΩcm. In addition, the auger electron spectroscopy (AES) analysis showed that TiN film deposited by ULET PEALD has lower impurity content than TiN films deposited by PEALD.