Discussion on microstructure of chemical-vapor-deposited TiN films based on the calculated gaseous concentration distrib
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TiN films were chemical-vapor-deposited on the inner wall of a tubular reactor. Films deposited in the upstream region of the reactor consisted of small and sharp crystals with (lll)-preferred orientation or random orientation. On the other hand, films deposited in the downstream region or at lower partial pressure of TiCl4 consisted of columnar crystals with (HO)-preferred orientation, having polyhedral shapes on the surface. For the films deposited under different conditions at different axial positions, relationships were investigated among the temperature, the calculated concentrations on the substrate, and the degree of preferred orientation of the films. As a result, it was shown that formation of films with (llO)-preferred orientation is related to the conditions of high temperature and low partial pressure of TiCU. Films deposited at the higher gas flow rate had lower degrees of (HO)-preferred orientation. Decrease in partial pressure of TiCl4 along the axial direction in the reactor was calculated to be smaller at higher gas flow rate, and provided suitable conditions for deposition of films having small and sharp crystals. I. INTRODUCTION In the chemical vapor deposition (CVD) process, film microstructures and depositions rates have to be controlled in order to obtain the desired film properties1 and the homogeneous distribution of film thickness.2 In general, this is accomplished by selecting the operation conditions of the CVD process, such as the substrate temperature, gas flow rate, gas pressure, and gas compositions. There are many reports on the relationship among the operation conditions, the microstructure of films,3"5 and the deposition rates.6~8 In this regard, it is possible to analyze the deposition rate of films by specifying the local deposition conditions in the reactor, such as the temperature and concentration in the gas phase above and on the substrate, either experimentally of by calculating the flow and mass transfer. Many studies are reported9"12 that discuss the film thickness distributions in the reactor quantitatively. On the other hand, there are many factors to characterize the film microstructures, such as grain size, morphology, crystal orientation, etc., which have their own dependence on the local deposition conditions.13 Consequently, qualitative discussions have been made on the relation between the CVD operation conditions and the formation of film microstructures.614 It is of interest to investigate the formation conditions of film microstructure, as quantitatively as possible by selecting specific parameters for describing film microstructures appropriately. CVD-TiN films have been used for protective coating of metallic materials,15 barrier layers in electronic J. Mater. Res., Vol. 10, No. 11, Nov 1995 http://journals.cambridge.org
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devices,16 and so on. It has been reported that crystal shape and microstructure of atmospheric pressure chemical vapor deposition (APCVD)-TiN films are dependent on the operation conditions 1718 sensitively. Therefo
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