Synthesis and characterization of low pressure chemically vapor deposited boron nitride and titanium nitride films
Committee for the Interdisciplinary Program in Materials Science and Engineering
Doctor of Philosophy
Materials Science and Engineering
Levy, Roland A.
Ravindra, N. M.
Grow, James M.
Ivanov, Dentcho V.
Low Pressure Chemically Vapor Deposited Films
This study has investigated the interrelationships governing the growth kinetics, resulting compositions, and properties of boron nitride (B-C-N-H) and titanium nitride (Ti-N-Cl) films synthesized by low pressure chemical vapor deposition (LPCVD) using ammonia (NH3)/triethylamine-borane and NH3/titanium tetrachloride as reactants, respectively.Several analytical methods such as the FTIR, UVNisible spectroscopy, XPS, AES, RBS, SEM, and XRD were used to study the stoichiometry and structure of the deposited films.
The B-N-C-H films were synthesized over a temperature range of 300 to 8500C at various flow rate ratios of the reactants and total pressure range of 50 to 150 mTorr. The deposits were amorphous in all cases having an index of refraction ranging between 1.76 and 2.47 depending on the composition of the films. The stress of the deposited films varied from +240 to -200 Wa, depending on the deposition parameters. The hardness and Young's modulus were found to be between 5 to 12 GPa and 50 to 120 GPa, respectively. Electrical properties of the BN films were measured using metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) structures. The films did not react with water vapor and exhibited dielectric constant between 3.12 and 5.5. Free standing X-ray windows with thickness varying from 2000Å to 12,000Å, were fabricated using the mildly tensile and compressive films and X-ray transmission studies through these windows indicate significantly lower absorption when compared to the commercially available polymeric X-ray windows.
The Ti-N-Cl deposits exhibited an Arrhenius d ependence in the deposition temperature regime of 450 to 600 °C from which an activation energy of ~42 kJ/mol was calculated. The growth rate dependencies on the partial pressures of NH3 (50 to 100 mTorr) and TiC14 (1 to 12 mTorr) yielded reaction rate orders of 1.37 and -0.42 respectively. Films with compositions trending towards stoichiometry were produced as the deposition temperature was decreased and the NH3 partial pressure was increased. The chlorine concentration in the films was observed to decrease from ~8 % (a/o) at the deposition temperature of 450 °C down to ~0.2 % (a/o) at 850 °C. The film density values increased from 3.53 to 5.02 g/cm3 as the deposition temperature was increased from 550 to 850 °C. The resistivity of the films was dependent on changes in deposition temperature and flow rate ratios. The lowest resistivity value of 86 µΩcm was measured for a deposition temperature of 600°C and an NH3/TiCl4 flow ratio of 10/1. The film stress was found to be tensile for all deposits and to decrease with higher deposition temperatures. Nanoindentation measurements yielded values for the hardness and Young's modulus of the films to be around 15 and 250 GPa, respectively. X-ray diffraction measurements revealed in all cases the presence of cubic TiN phase with a preferred (200) orientation. For the investigated aspect ratios of up to 4: 1, the deposits were observed to exhibit conformal step coverage over the investigated range of processing conditions.
njit-etd2000-029 (203 pages ~ 10,499 KB pdf)
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Created May 31, 2002