Thin Film Properties of LPCVD TiN Barrier for Silicon Device Technology
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THIN FILM PROPERTIES OF LPCVD TiN BARRIER FOR SILICON DEVICE TECHNOLOGY RAMA I. HEGDE, ROBERT W. FIORDALICE, EDWARD 0. TRAVIS AND PHILIP J. TOBIN
Advanced Products Research and Development Laboratory, Motorola, Inc., 3501 Ed Bluestein Boulevard, Austin, Texas 78721
ABSTRACT Thin film properties of LPCVD TiN barriers deposited on Si(100), using TiCl4 and NH3 as reactants, were investigated as a function of deposition temperature between 400 oC and 700 oC. The TiN film chemistry and film composition were studied by AES and RBS techniques, while the microstructural properties (grain size, lattice parameter and texture) were evaluated by XRD. The TiN deposition rates and film resistivities were also determined. Finally the film properties of the TiN barriers as determined by surface analysis were related to the process parameters.
INTRODUCTION In the microelectronics industry titanium nitride (TIN) is primarily used as a barrier layer to prevent interdiffusion of silicon and aluminum metallization, and as an adhesion layer prior to LPCVD blanket tungsten deposition [1 - 8]. Conventionally, TiN films are deposited by reactive sputtering or, by thermal nitridation of sputtered titanium layers. As integrated circuit (IC) feature sizes shrink to deep submicron dimensions, films produced by these techniques suffer from poor step coverage, especially in submicron contact holes with high aspect ratios, causing barrier and adhesion properties to degrade. However, TiN films produced by low pressure chemical vapor deposition (LPCVD TiN) provide excellent step coverage and good diffusion barrier characteristics [1 - 8]. EXPERIMENTAL LPCVD TiN depositions were carried out in a rapid thermal chemical vapor deposition (RTCVD) system, which is a load locked, single-wafer cold wall reactor, with linear cassette to cassette wafer transfer. The substrate is radiantly heated from the backside. A thermocouple in contact with the center of the substrate's
Mat. Res. Soc. Symp. Proc. Vol. 250. P1992 Materials Research Society
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backside provides closed loop temperature control within + 1% of set point. TiN depositions on Si were carried out between 400 oC and 700 oC using TiCl4 and NH 3 reactants with Ar as a carrier gas. TiN films were characterized by Auger electron spectroscopy (AES), Rutherford backscattering (RBS), x-ray diffraction (XRD) and transmission electron microscopy (TEM). Oxygen and carbon contents were determined from AES. Chlorine levels were determined by both AES and RBS. Sheet resistance of the films was measured with a Prometrix four point probe. Film resistivities were derived from the sheet resistances and film thickness. Film thicknesses were measured by x-ray fluorescence and calibrated with cross-sectional TEM. Deposition rates were calculated from the thickness of deposited TiN film. RESULTS AND DISCUSSION
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Film chemistry
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An Auger spectrum (AES) of an LPCVD TiN film deposited at 650 oC is shown in Figure 1. The Auger peak intensities for Ti+N (380 eV), Ti (418 eV), 0 (503 eV), Cl (181 eV)
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