The Influence of Stress on The Growth of Titanium Silicide Thin Films on (001) Silicon Substrates
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S.L. CHENG*, S.M. CHANG*, H.Y H1UANG*, YC. PENG*, L.J. CHEN*, B.Y TSUI**, C.J. TSAI***, AND S.S. GUO*** *Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan, Republic of China, [email protected] "**Electronics Research and Service Organization, Industrial Technology and Research Institute, Hsinchu, Taiwan, Republic of China ***Institute of Materials Engineering, National Chung Hsing University, Taichung, Taiwan, Republic of China ABSTRACT
The influence of stress on the enhanced formation of C54-TiSi 2 phase has been investigated. Tensile stress induced by backside CoSi, film on the silicon substrate has been found to enhance the growth of C54-TiSi 2 on (001)Si. The thickness of amorphous interlayers (a-interlayers) between Ti films and silicon substrates was found to be thicker and thinner in the tensilly and compressively stressed samples, respectively. From auto-correlation function analysis, the thicker a-interlayer was found to consist of a higher density of crystallites. The crystallites provide nucleation sites for C49-TiSi 2 and facilitate the formation of C49-TiSi, of small size. The larger total area of C49-TiSi2 grain boundaries supplies more nucleation sites for the phase transformation of C49- to C54-TiSi 2. Therefore, the tensile stress present in the
silicon substrate promotes the formation of a-interlayer and decreases the grain size of C49TiSi2, which increases the nucleation density of the C54-TiSi 2 phase. As a result, the transformation of C49- to C54-TiSi 2 phase is enhanced. INTRODUCTION
Among metal silicides, C54-TiSi2 has the best combination of a low resistivity (15-20 ý.Qcm), low silicon consumption, good thermal stability, high conductivity and low electrical leakage- For these reasons, C54-TiSi2 has been widely used as electrical contact to Si to reduce contact and series resistance in electronic devices [1]. However, as the linewidth of a device structure is scaled down to deep submicron region, problems related to stresses can occur in semiconductor device fabrication. The stress generated in laterally confined areas on silicon substrate was found to influence significantly the growth kinetics of silicides [2-4]. Recently, the occurrence of an a-interlayer between Ti and Si substrate is speculated to act as a direct nucleation source for C54-TiSi 2, which enhances the phase transformation of C49- to C54-TiSi, Mat. Res. Soc. Symp. Proc. Vol. 564 © 1999 Materials Research Society
[5,6]. However, the influences of stress on the formation of the a-interlayer have not been investigated. In a previous study, the low-resistivity C54-TiSi2 phase transformation temperature in tensile stressed samples was found to lower by about 100 °C than that in compressively stressed samples [7]. The phases formed in samples annealed at different temperatures determined by sheet resistance measurements and grazing angle XRD are listed in Table I. In the present work, mechanism of enhanced formation of C54-TiSi 2 by applied stress on (001)Si is clarified. T
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