According to the original literature, titanium nitride is a compound with the molecular formula of TiN and the molecular weight of 6 1.88. It is also a golden yellow material. However, when the thickness of titanium nitride film changes with the change of process conditions, its color will also change accordingly.

Generally speaking, when the thickness of titanium nitride film is about 200 nanometers, the color is golden yellow. But with the increasing thickness, the color will gradually turn purple. Therefore, if the surface color of titanium nitride is purple, it is a normal phenomenon because the thickness of titanium nitride film changes.