Titanium nitride (TiN) is used as a metal gate in complementary metal-oxide-semiconductor (CMOS) technology as it has low resistivity and is compatible with gate dielectrics.1 TiN is also deposited as a wear resistant coating, and barrier layer for copper diffusion due to its chemical and thermal stability.2 Traditionally TiN was deposited using physical vapour deposition techniques which suffer from a poor step coverage in deep contacts and via trenches due to the shadowing effects especially in high aspect ratio structures.
Atomic layer deposition (ALD) is a thin film deposition technique which allows for Å-level control of the film thickness, excellent uniformity, and conformal coating of high aspect ratio features. The deposition of thin films of TiN by ALD has been reported using various precursors such as titaniumtetrachloride (TiCl4),3 and tetrakis (dimethylamino) titanium (Ti(N(CH3)2)4, TDMAT).2, 4, 5
Nevertheless, optimization of film growth and the electrical properties and their uniformities are often required. Ideally, non-destructive characterisation of thickness and electrical uniformity across the entire surface covered by the deposition can be done to ensure the quality of the final film. This white paper will demonstrate a non-destructive electrical characterisation of plasma atomic layer deposited TiN on 200 mm wafers using THz Spectroscopy.