Ion-assisted chemical vapor deposition of thin film cubic boron nitride.

摘要

In this thesis, a new arcjet ion-assisted chemical vapor deposition (IACVD) process was developed along with diagnostic techniques to investigate the growth of thin films of cubic boron nitride (c-BN). The objective was to gain a better understanding of the physical limitations of the IACVD process, to successfully quantify some of the parameters which control c-BN growth and to characterize the material properties of the c-BN films.; To better characterize ion bombardment at the biased substrate in the vapor deposition reactor, a retarding potential analyzer (RPA) was designed and implemented to measure the ion flux, the electrical sheath thickness at the substrate, and the energy distribution of the ion beam bombarding the growing film. The dependence of the ion energy distribution, and thus c-BN deposition, on various process parameters was investigated. To verify the RPA measurements, monte carlo calculations were performed to simulate the transport of ions across the sheath and to calculate the ion energy distribution.; In order to characterize the c-BN films grown in this study, several spectroscopic diagnostics were utilized. A damped classic oscillator model was developed to provide quantitative values for volumetric phase fractions and film thickness from infrared transmission spectra of the boron nitride films. X-ray photoelectron spectroscopy (XPS) characterization of the BN films was performed to determine atomic concentrations in the films and as a fingerprint for sp{dollar}sp2{dollar} bonding through identification of a {dollar}pi{dollar} plasmon spectral feature. Near edge x-ray absorption fine structure (NEXAFS) spectroscopy was used to verify the calculated c-BN content in the films obtained by the model fits of IR transmission spectra. This verification was performed through the identification of distinct NEXAFS spectral features caused by sp{dollar}sp3{dollar} and sp{dollar}sp2{dollar} bonding in the films. The study was concluded with the discussion and application of a multi-layer growth, stress-induced phase change theory for the deposition of c-BN films. Using the conceptual backbone of this theory, a first order model for the thermodynamic energy balance on a growing c-BN film was developed. The model predicts that film stress, and thus c-BN growth, is dependent on the ion momentum flux at the growth surface.