Ni Silicide Formation on Polycrystalline SiGe and SiGeC Layers
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Ni Silicide Formation on Polycrystalline SiGe and SiGeC Layers Erik Haralson, Tobias Jarmar1, Johan Seger, Henry H. Radamson, Shi-Li Zhang, Mikael Östling Kungl Tekniska Högskolan, Department of Microelectronics and Information Technology, Electrum 229, SE-164 40, Kista, Sweden 1 Uppsala University, The Ångström Laboratory, Box 534, SE-751 21, Uppsala, Sweden ABSTRACT The reactions of Ni with polycrystalline Si, Si0.82Ge0.18 and Si0.818Ge0.18C0.002 films in two different configurations during rapid thermal processing were studied. For the usually studied planar configuration with 20 nm thick Ni on 130-290 nm thick Si1-x-yGexCy, NiSi1-xGex(C) forms at 450oC on either Si0.82Ge0.18 or Si0.818Ge0.18C0.002, comparable to NiSi formed on Si. However, the agglomeration of NiSi1-xGex(C) on Si0.818Ge0.18C0.002 occurs at 625oC, about 50oC higher than that of NiSi1-xGex on Si0.82Ge0.18. For thin-film lateral diffusion couples, a 200-nm thick Ni film was in contact with 80-130 nm thick Si1-x-yGexCy through 1-10 µm sized contact openings in a 170 nm thick SiO2 isolation. While the Ni3Si phase was formed for both the Si0.82Ge0.18 and Si0.818Ge0.18C0.002 samples, the presence of 0.2 at.% C caused a slightly slower lateral growth. INTRODUCTION The use of SiGe for the production of high-speed electronic devices has become mainstream in the past several years. One advancement that has helped to extend the capabilities of SiGe for high-speed heterojunction bipolar transistors (HBT) has been to use substitutional C to allow for incorporation of more Ge into the strained single-crystal intrinsic base region and to improve the definition of sharp and high doping profiles through limiting the dopant diffusion, especially the transient enhanced diffusion. In differential-base HBT designs the polycrystalline extrinsic base region is simultaneously grown with the intrinsic base [1]. While the substitutional C helps enhance device performance of high-speed HBTs such as these, it may also act as an impurity, detrimental to the formation of silicided contacts on the polycrystalline extrinsic base region. NiSi is very promising as a contact material for deep submicron circuits due to its lowtemperature and linewidth-independent formation [2]. In the present study, Ni is chosen because the desired low-resistivity mono-germanosilicide Ni(Si,Ge) shares the same crystallographic structure as NiSi [3,4]. It also forms at comparably low temperatures as NiSi does. The frequently used CoSi2 is not considered because its formation becomes increasingly difficult in the presence of Ge due to thermodynamic effects [5]. The incorporation of C further increases the formation temperature for CoSi2 [6]. With the introduction of low-temperature backend processing the stability of Ni(Si,Ge) is less problematic than previous. Therefore, the reaction of Ni with polycrystalline Si1-xGex and Si1-x-yGexCy is investigated in this work. EXPERIMENTAL Two sets of samples were prepared and analyzed. In the first set polycrystalline Si, Si0.82Ge0.18, and Si0.818Ge0.1
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