Nickel, Platinum and Zirconium Germanosilicide Contacts to Heavily Phosphorous Doped Silicon-Germanium Alloys for Advanc
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Nickel, Platinum and Zirconium Germanosilicide Contacts to Heavily Phosphorous Doped Silicon-Germanium Alloys for Advanced CMOS Source/Drain Junctions Hongxiang Mo, Jing Liu, and Mehmet C. Öztürk North Carolina State University, Department of Electrical and Computer Engineering Centennial Campus, EGRC Building, Box 7920, Raleigh, NC 27695-7920 ABSTRACT As the MOSFET dimensions continue to shrink, source/drain contact resistance is emerging as the dominant component of the MOSFET parasitic series resistance. To meet the series resistance requirements of future MOSFETs, contact resistivity values near 10-8 ohm-cm2 are required. Selective Si1-xGex source/drain technology has been proposed as an alternative to ionimplantation to form the ultra-shallow junctions of future CMOS technology nodes. One of the key advantages of this technology is the smaller band gap of Si1-xGex, which provides a smaller contact barrier height, an essential requirement for reducing the contact resistivity. We have previously reported low-resistivity of Ni germanosilicide NiSi1-xGex and Pt germanosilicide PtSi1-xGex contacts to boron doped Si1-xGex alloys. In this work, Zr germanosilicide, Zr(Si1xGex)2 was considered as an alternative material with a higher thermal stability than Ni and Pt germanosilicides. The contact resistivity values for different contact materials were measured using four-terminal Kelvin structures. The results from this work show that both Zr and Pt germanosilicides yield high contact resistivity values around 10-7 ohm-cm2. On the other hand Ni germanosilicide contacts can reach 10-8 ohm-cm2 with further improvements using a thin layer of Pt under Ni.
INTRODUCTION Si1-xGex source/drain technology was proposed as an alternative junction and contact formation scheme to meet the requirements of CMOS technology nodes beyond 70 nm [1,2]. The technology is based on selective chemical vapor deposition of in-situ boron or phosphorus doped Si1-xGex in source/drain areas. The fact that dopant atoms occupy substitutional sites during growth make high temperature activation anneals unnecessary. Since the films are typically deposited in the temperature range of 500-750°C where dopant diffusion is virtually nonexistent, super abrupt junctions can be formed. As deposited, the films provide resistivity values that can meet extension sheet resistance requirements of all technology nodes included in International Technology Roadmap for Semiconductors (ITRS). Furthermore, the smaller bandgap of Si1-xGex results in a smaller Schottky barrier height, which can translate into significant reductions in contact resistivity due to the exponential dependence of contact resistivity on barrier height. Previous work in this laboratory showed that low-resistivity Ni and Pt germanosilicide contacts (ρc ~ 10-8 ohm-cm2) can be formed on boron doped Si1-xGex alloys. In this work, we report experimental results from recent work on characterization of germanosilicide contacts formed on phosphorus doped Si1-xGex alloys.
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