Kinetics of reactions of Ni contact pads with Si nanowires
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Sharis Minassian Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802
Chito Kendrick and Suzanne E. Mohneya) Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (Received 26 January 2011; accepted 20 May 2011)
For development and integration of Si nanowires into nanoelectronic devices, an understanding of Ni silicide formation in electrical contacts to Si nanowires is necessary. Here, we examine the kinetics of Ni silicide phase formation. For Si nanowires with [111] growth directions, NiSi2 is the only phase to form in the temperature range 400–550 °C, and the NiSi2 growth exhibits linear kinetics from 400 to 500 °C with an activation energy of 0.76 6 0.10 eV. In the case of Si nanowires with [112] growth directions, growth of the h-Ni2Si phase in contact with the Si nanowire occurs with parabolic kinetics over the temperature range 400–550 °C, and an activation energy of 1.45 6 0.07 eV/atom is extracted. Differences in the growth rates for Ni silicide phases with different SiNW growth directions implies that for simultaneous preparation of SiNW devices with Ni silicide contacts, SiNWs with the same growth direction are necessary.
I. INTRODUCTION
Silicon nanowires (SiNWs) have attracted considerable interest for a variety of applications including field-effect transistors,1 thin-film transistors,2 and chemical and biological sensors.3 For optimal device performance there is a need for low resistivity, thermally stable contacts to the nanowires. Currently, NiSi is commonly used as the contact to complementary metal–oxide semiconductor (CMOS) devices because of its low resistivity and relatively low consumption of Si compared to other attractive metal silicide phases.4 Current and future CMOS device designs including fin field-effect transistors are geometrically very similar to nanowire devices. Therefore, the formation of Ni silicides in contact to SiNWs is of technological interest both for continued scaling of CMOS technology and for the many potential applications of Si nanowire devices. To date, there have been a number of studies on the reaction of Ni with SiNWs; however, widely varying results have been obtained.5–12 In some of these studies, the Ni silicide phase formed has not been conclusively identified. In others, different Ni silicide reaction products have been identified, including Ni31Si12,8 d-Ni2Si,8,11 h-Ni2Si,11,12 Ni3Si2,11 NiSi,5–7,10–12 and NiSi2.8,9,12 In studies by Tu and coworkers,5–7 the point contact reaction Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.188 J. Mater. Res., Vol. 26, No. 17, Sep 14, 2011
http://journals.cambridge.org
II. EXPERIMENTAL
Samples were fabricated by a method described previously,12 with the lone exception being that the backside of the wafer was not etched away because of the use of fieldemission scanning electron microscopy (FESEM; Leo 1530)
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between NiNWs and SiNWs with [111] growth di
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