Alternate Titanium Source Compounds for CVD of Ti/TiC Coatings
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ALTERNATE TITANIUM SOURCE COMPOUNDS FOR CVD OF Ti/TiC COATINGS.
THOMAS J. GROSHENS*, CHARLOTTE K. LOWE-MA, RICHARD C. SCHERI, AND ROBERT Z. DALBEY. Research Department, Naval Air Warfare Center, Weapons Division, China Lake, CA 93555
ABSTRACT CVD experiments were conducted using (Me 3 SiCH 2 )4 Ti, Bis(2,4-dimethylpentadienyl) titanium, CI3TiMe, (Me 3SiCH 2 ) 2 TiCl 2 , and Me 3SiCH 2 TiCl 3 to evaluate their potential as Ti precursor compounds. Only Me 3 SiCH 2 TiCI 3 was suitable for atmospheric CVD applications. Uniform thin films of polycrystalline TiC were deposited using Me 3 SiCH 2 TiC13 in an argon ambient between 700 'C and 800 'C. A mechanism involving initial loss of Me 3 SiCl to generate a titanium carbene intermediate is proposed. Thin films of TiC deposited on Si[l 111] were characterized using XRD and AES. Depth profile line shape analysis showed only TiC and elemental Si in the interfacial region. XRD indicates some titanium silicide is formed at 800 'C. In a hydrogen ambient, hydrogenolysis of the alkyl group occurs and very poor film growth results were obtained.
INTRODUCTION 2 1 Titanium carbide is an extremely hard material (Vickers hardness 2988 kgf mm- ) with a high melting point (3340 K), corrosion resistant, and highly conductive (specific resistivity 50 gi cm) 2 . Because of these physical properties thin films of TiC have potential uses as a 5 4 diffusive barrier 3 , electrical contact material , and tribological coatings . Chemical vapor deposition (CVD) methods for producing TiC films have been demon6 strated using TiCI4/IH2 and methane, ethane, CCI4 , or other hydrocarbons . These methods 7 require substrate temperatures above 1000 'C. Recently, Girolami et al. reported deposition of TiC at temperatures as low as 150 'C from tetraneopentyltitanium using low pressure CVD methods. However, this solid single-source precursor is limited to low pressure applications and its high melting point of 99 'C could result in vapor transport problems. It is also reported 8 to be thermally unstable at room temperature over long periods of time (>1 week) . Our objective was to develop a liquid, single source precursor capable of depositing TiC using atmospheric pressure CVD methods at lower temperature than current methods. We investigated a number of known organotitanium compounds as possible precursors using the physical state, long term stability, and vapor pressure as criteria to select the compounds to be evaluated.
EXPERIMENTAL 9 12 Small samples (1-5 g) of the compounds were prepared by published methods - . Larger samples of Me 3 CH 2TiCI3 were conveniently prepared from the reaction of (Me 3 SiCH 2 )4 Ti with TiCI 4 or of neat (Me 3 SiCH 2 )2 Zn with excess TiC14 . Deposition experiments were conducted using suitable candidates in an ersatz CVD reactor. A detailed description of the 13 reactor design is provided by Lee et al. . Zero grade argon or hydrogen carrier gases were used without further purification. Quartz was used as a substrate for initial deposition Mat. Res. Soc. Symp. Proc.
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