Control and monitoring of growth of chromium nitride coatings using in-situ spectroscopic ellipsometry

In-situ spectroscopic ellipsometry (SE) in the energy range from 1.5 to 5.5 eV was used to monitor the deposition of chromium nitride coatings deposited by ion-assisted reactive magnetron sputtering. First, a systematic study was conducted on monolithic coatings as a function of each of the following deposition parameters: nitrogen flow rate, bias voltage, and target current. In-situ ellipsometry data were analyzed and the composition of the coatings identified as a function of these parameters. Two additional samples were deposited using arbitrary initial deposition conditions and in-situ ellipsometry was used as a diagnostic tool that quickly indicated the required nitrogen flow rate adjustments to be made in order to produce stoichiometric CrN and Cr2N coatings. These samples were tested using X-ray diffraction (XRD) and ex-situ SE. Results derived from XRD and SE data correlated well and confirmed the growth of stoichiometric phases. Finally, in-situ ellipsometry was used to monitor the early stages of film growth and graded interfaces in CrN/Cr2N multilayer structures. The coalescence thickness of CrN on Si and the thickness of the graded region in multilayers were determined. In-situ ellipsometry was shown to be a production worthy technique for process monitoring and control of chromium nitride single and multilayer structures.