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1070-E02-09

Pt Segregation at the NiSi/Si Interface and a Relationship with the Microstructure of NiSi Haruko Akutsu1, Hiroshi Itokawa1, Kazuhiko Nakamura1, Toshihiko Iinuma1, Kyoichi Suguro1, Hiroshi Uchida2, and Masanori Tada2 1 Toshiba Corporation Semiconductor Company, 8, Shinsugita-Cho, Isogo-Ku, Yokohama, Japan 2 Toshiba Nanoanalysis Corporation, Japan ABSTRACT Platinum Segregation at the NiSi/Si Interface and a relationship with the microstructure of NiSi were studied. We investigated the Platinum distribution by using TEM, EDX and Atomprobe. We found Pt segregation at the grain boundary of NiSi. And we studied shapes of NiSi(without Pt) grains and Pt doped NiSi grains by using SEM. The SEM apparatus has an angle selective Backscattered electron detector. (ASB detector) The ASB detector was adjusted to get channeling contrast. We found that a Pt doped NiSi grain is smaller than a NiSi grain. INTRODUCTION The purpose of using Nickel monosilicide (NiSi) is lowering the resistances of doped Si layers. However NiSi is not thermally stable. D. Mangelinck et al. found that Pt doped Nisilicide has rather good tolerance of thermal agglomeration and morphology. [1] [2] Several possible mechanisms have been reported to play a role in the improved thermal stability of the NiSi:(1) the addition of Pt appears to influence the texture of NiSi film, thus affecting the interface energy, (2) the expansion of the NiSi lattice due to the additioin of Pt may result in the transformation of the MnP-type structure into more stable NiAs-type structure, and (3) since Pt is insoluble in NiSi2 , the nucleation of NiSi2 will be more difficult because of the required expulsion of Pt from the nucleation region and the resulting change in entropy of mixing. [1] [3] On another front, T.F.Kelly et al. analyze Ni(Pt)Si/Si(As doped) interface with Atom Probe. They found the As segregation at the NiSi/Si interface and the Pt segregation of the surface in the 1-D profile. [4] We first reported the Pt segregation was found at a NiSi/Si interface by AP analysis. [6] In this study, we studied a precise Pt distribution and a difference between NiSi with Pt and NiSi without Pt. First we investigated the Pt distribution with Atomprobe, TEM and EDX. Second we observed NiSi and Ni(Pt)Si films by using a SEM with angle selective Backscattered electron detector. Finally we discuss that the Pt distribution and its role. EXPERIMENT Ni-Pt alloy film of 8-12nm in thickness were deposited on As implanted (100)Si substrates. Some of the samples were annealed to form Ni silicide in N2 after Ni sputtering. As deposited sample(sample A) and the sample after silicidation (sample B) were prepared for AP analysis using LEAP3000(IMAGO) with a special resolution of 0.4 nm×0.4 nm×0.2 nm , detection efficiency about 50 atomic % and sensitivity about 0.5atomic %. To complement TEM, FE-SEM observation was carried out. Figure 1(a) shows the depth profile through the Ni(Pt)/Si interface analyzed by AP. Z=0nm is Ni =50% isosurface. Fig. 1(b) shows that of sample B. Z=0nm is