OPTICAL-EMISSION SPECTROSCOPY ON AN INDUSTRIAL PACVD SYSTEM FOR TITANIUM NITRIDE

The optical emission spectra of an industrial PACVD process for coatin g of hard metal and HSS tools with titanium nitride (TiN) layers by a micro-pulsed d.c. discharge were investigated. For recording of the sp ectra a simple and economy-priced spectrometer with an resolution of a bout 0.5 nm was used. Atomic lines of H, Ar and Ar+, and some molecula r bands of H-2, N-2, N-2(+) and NH were found. With the resolution and sensitivity available it was not possible to clearly identify atomic lines of titanium, nitrogen or chlorine and bands of titanium nitride or titanium chlorides. Because the optical emission of the discharge c omes only from species made up of five elements one can expect that ma ny of the spectral lines are highly correlated. For that reason, princ ipal component analysis should offer a good tool to identify those par ts in the optical emission spectra which distinguish the single spectr a, and which would be relevant for plasma monitoring. However, factors describing species responsible for TiN formation were not found withi n our experimental limits.