Chemical vapor deposition synthesis and characterization of co-deposited silicon-nitrogen-boron materials
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Chemical vapor deposition synthesis and characterization of co-deposited silicon–nitrogen–boron materials A. Essafti D´epartement de Physique, Facult´e des Sciences Semlalia, B.P. S15, Universit´e Cadi Ayyad, Marrakech, Morocco
C. G´omez-Aleixandre Instituto de Ciencia de Materiales, CSIC, Universidad Aut´onoma, C 12, Cantoblanco, 28049 Madrid, Spain
J. L. G. Fierro Instituto de Cat´alisis y Petroleoqu´ımica, CSIC, Cantoblanco, 28049 Madrid, Spain
M. Fern´andez and J. M. Albella Instituto de Ciencia de Materiales, CSIC, Universidad Aut´onoma, C 12 Cantoblanco, 28049 Madrid, Spain (Received 30 November 1995; accepted 1 June 1996)
Si–N–B films have been deposited by LPCVD from SiH4yB2 H6yNH3 gas mixtures. The influence of the temperature and the composition of the gas mixture on the deposition process and film properties has been investigated. At 1000 ±C, for the highest ammonia flow rate (SiH4 : B2 H6 : NH3 , 10 : 25 : 500), a mixture of turbostratic boron nitride and silicon nitride was deposited. For decreasing ammonia flow rates the Si –N–B ternary system was formed (1260 cm21 band in the infrared spectra), which co-exists with the unstable turbostratic boron nitride structure. Finally, for a low NH3 flow rate of 100 sccm, stable amorphous films are obtained. On the other hand, at 800 ±C, stable films with a high content in the ternary Si–N –B compound were obtained for a wide range of ammonia concentrations (100–500 sccm). At this temperature (800 ±C), the composition of the films, as measured by Auger and photoelectron spectroscopies, strongly depends on the [SiH4 ]y[B2 H6 ] ratio in the gas mixture. The improvement in the mechanical and chemical properties of the samples has been associated with the increase in the content of Si–N bonds in the Si–N –B films.
I. INTRODUCTION
There is a growing interest in the synthesis of boron nitride crystallized in the zinc blende structure (c-BN) for applications as hard and optical coating material. However, due to the difficulties in obtaining the crystalline form, amorphous boron nitride films are usually deposited by CVD techniques, from the reaction of diborane and ammonia. These films are routinely used as insulating material as well as a protective coating in microelectronic circuits in order to provide protection against metal scratches during handling.1 At present, much effort is also being devoted to the preparation by CVD of BN-based materials (ternary X–N –B compounds with X Si, C, etc.) through a co-deposition process using several source gases simultaneously.2 Besides the intrinsic interest of these amorphous products, they can also be crystallized by high-pressure treatments, in order to obtain c-BN-based composites for industrial applications. In previous works we have reported the effect of the r [B2 H6 ]y[NH3 ] ratio in the gas mixture as well J. Mater. Res., Vol. 11, No. 10, Oct 1996
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as the deposition temperature on the mechanism of the B2 H6 1
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