Epitaxial Growth of Near Noble Silicides on (111)Si by Rapid Thermal Annealing
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EPITAXIAL GROWTH OF NEAR NOBLE SILICIDES ON (IIU)Si BY RAPID THERMAL ANNEALING H.C. CHENG*, I.C. WU**, AND L.J. CHEN** * Department of Electronics Engineering, National Chiao Tung University, Hsinchu, Taiwan, Republic of China. ** Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.
ABSTRACT The epitaxial growth of near noble silicides, including CoSi , NiSi 2 , FeSi , Pd 2 Si, and PtSi on (lll)Si, by rapid thermal annealing was studied by Single-crystalline CoSi2 was formed on transmission electron microscopy. (111)Si in the solid phase epitaxy regime by a non-ultra-high vacuum method. The effect on gas ambient was found to be of critical importance on the The best NiSi 2 , FeSi , Pd Si, growth of single-crystal CoSi on (lll)Si. by rapid thermal annealIng were found to and PtSi epitaxy grown on (ll)Si be of comparable quality to those grown by conventional furnace annealing.
INTRODUCTION Metal silicides have received increasing attention for the metallization of microelectronics devices in recent years, particularly as gate For contacts to shallow junctions, it is electrodes and contacts [1,2]. necessary to have a smooth interface between the silicide and silicon, and a Because of the long annealing time, minimal change in the dopant profile. conventional furnace annealing has the following degrading effects: (1) dopant diffusion in the source/drain regions, (2) outdiffusion of dopants from the polysilicon layer, and (3) lateral growth of the silicides due to the significant lateral silicon motion, causing short circuits between the Rapid thermal annealing (RTA) is often source/drain and the gate [3]. utilized to circumvent these limitations. Epitaxial silicides have attracted much interest in the past few years for their key roles in gaining fundamental understanding of the electronic properties associated with the metal/silicon interfaces as well as potential applications in fabricating novel classes of devices employing buried siligroup of silicides cide layers [4-6]. Near noble silicides were the first to be shown to grow epitaxially on silicon by conventional furnace annealing [1,2]. Attempts were also made to grow epitaxial silicides on silicon in both the solid and liquid phase epitaxy regimes by transient thermal Most of these films were characterized by Rutherford annealing [7-11]. backscattering-channeling technique, which, although powerful in determining the overall quality of the silicide overlayer, is not well suited for In this paper, we report a transmission microstructural characterization. electron microscope (TEM) study of the epitaxial growth of near noble silicides on silicon by rapid thermal annealing.
EXPERIMENTAL PROCEDURES cleaned chemically 3-5 9-cm, n or p type (lll)Si wafers were first The samples were etched in a buffered HF with the usual procedures. solution (HF:H 0 = 1:50) for 2 min. immediately before loading into an Ni, Co, Pd, Pt or Fe thin films, 30 nm in electron gun deposition chamber. thickness, were electron-g
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