Epitaxial Growth of Platinum-Group Metal Silicides on (111) SI
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Y.S. CHANG, J.J. CHU, and L.J. CHEN Department of Materials Science and Engineering National Tsing-Hua University, Hsinchu, Taiwan, ROC Epitaxial ruthenium, osmium, rhodium and iridium silicides have been successfully grown on silicon. Electroless chemical plating was used to deposit platinum-group metal thin films on silicon. Two step annealing was found to be effective in inducing the growth and improving the quality of the epitaxial silicide on silicon. Transmission electron microscopy was applied to characterize the microstructures and determine the orientation relationships between epitaxial silicides and substrate Si. The compositions of deposited films were determined by scanning Auger electron spectroscopy combined with depth profiling technique. The percentages of phosphorus were found to be in the range of 2-3 at. %. INTRODUCTION Epitaxial metal silicides have attracted much attention for their potential applications in novel devices as well as for the fundamental understanding of the characteristics of silicide/Si system in recent years.E1-4] Before 1983, there were only four generally known epitaxial silicides, i.e. PtSi, Pd 2 Si, NiSi 2 , and CoSi2 . In the last two years, a number of refractory metal silicides, FeSi 2 and MnSil.7 were found to grow epitaxially on silicon.[5-13] Encouraged by the apparent universality of the epitaxial silicide formation in transition metal -silicon system, attempts were made to grow platinum-group silicides epitaxially on silicon. Because of the enormous cost factor involved in depositing platinum-group metals on silicon by physical vapor deposition methods, a simple and economical electroless immersion plating method was adopted to deposit metal films on silicon.E14] Epitaxial NiSi 2 was previously found to grow on silicon in an electroless chemical immersion deposited Ni thin film on silicon system.[15] In this paper, we report the epitaxial growth of ruthenium, osmium, rhodium and iridium silicides on silicon. EXPERIMENTAL 3-5 ohm-cm, n-type,(111) Si wafers, 15 mil in thickness, were first cleaned chemically with the usual procedures. The samples were dipped in dilute HF solution (HF:H 20 = 1:50) for two minutes and then directly inserted into the electroless plating bath. The dipped wafers were immersed in a special hypophosphite-based electroless plating bath of platinum-group metals for a few minutes to deposit platinum-group metal thin film autocatalytically at about 900C. To minimize contamination from
Mat. Res. Soc. Symp. Proc. Vol. 54. ý1986 Materials Research Society
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impurities, the electroless deposition bath was prepared by using high purity reagents of deionized water produced from reverse osmosis deionization (18 M ohm-cm) followed by two-stage quartz distillation. The depositions were performed in a class 100 clean room. The whole process was carried out without drying the wafer surface until the plating was completed to protect the Si surface from oxidation and staining. The pH value of the bath was maintained to be 9 during deposition. The
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