Phase Transition and Formation of TiSi 2 Codeposited on Atomically Clean Si(111)
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PHASE TRANSITION AND FORMATION OF TiSi 2 CODEPOSITED ON ATOMICALLY CLEAN Si(111). Hyeongtag Jeon, Y. S. Cho*, E. Y. Kang, J. W. Park, and R.J. Nemanich** Department of Metallurgical Engineering, Hanyang Univ. Seoul, Korea 133-791. * Hyundai Electronics Industries Co., Ltd. Icheon Korea. ** Department of Physics, North Carolina State University, Raleigh, NC 27695
Abstract In this study, the phase transformation and the surface and interface morphologies of TiSi2 formed on atomically clean Si substrates are investigated. 200A Ti and 400A Si films on Si(1 11) have been co-deposited at elevated temperatures (400*C - 800*C) in ultrahigh vacuum. The phase transition of TiSi2 is characterized with using XRD. The results distinguish the formation of the C49 and C54 crystalline titanium silicides. The surface and interface morphologies of titanium silicides have been examined with SEM and TEM. A relatively smooth surface is observed for the C49 phase while a rough surface and interface are observed for the C54 phase. The islanding of the C54 phase becomes severe at high temperature (800 0 C). Islands of TiSi 2 have been observed at temperatures above 700°C but no islands are observed at temperatures below 600*C. For films deposited at 400TC and 500'C, weak XRD peaks corresponding to TiSi were observed and TEM micrographs exhibited small crystalline regions of titanium silicide at the interface.
Introduction Titanium silicide is often considered for application as contacts and interconnects due to its low resistivity and stability at high processing temperatures [1,2]. However, a significant problem in the application of titanium silicide is island formation, resulting in a rough surface morphology. Two different phases of TiSi2 have been reported after the reaction of Ti and Si [3]. These are TiSi2 of the C49 and C54 phases. The C49 phase of TiSi2 is formed at low temperatures, while higher temperature annealing leads to the transition to the C54 phase. Both strucumes are orthmihobic. The C49 phase is metastable forms at temperatures from 450 0C to 600TC. The stable C54 phase forms after higher temperature annealing to >6500 C. The initial intractions at temperatures below 450°C have also shown evidence of a disordered intermixed layer and in some cases the presence of additional silicides [4,5]. In this paper we focus on formation sequences and mechanism of the titanium silicides formed by codeposition of Ti and Si on atomically clean Si substrates at elevated temperatures. The surface and interface morphologies of the C49 and C54 TiSi2 phases were examined by SEM and TEM. The phases of titanium silicides were identified by XRD. Mat. Res. Soc. Symp. Proc. Vol. 311. 01993 Matedals Research Society
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Experimental The substrates used in this study were Si(1 11)-oriented substrates (25 mm diam.) with resistivities of 0.8-1.2 Qcm ( n-type, P-doped). The ultrahigh vacuum deposition chamber was equipped with a turbo-pumped loading chamber, and an ion-pumped deposition chamber. The deposition chamber has a heating stage and
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