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27 August 1997 Strained Si NMOSFET on relaxed Si1-xGex formed by ion implantation of Ge
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Abstract
Strained-Si films show considerably higher electron mobility than conventional silicon films which results in increased transconductance and drive current of strained-Si channel NMOSFETs. However, in order to form tensile strained silicon it is necessary to use relaxed Si1-xGex 'substrates,' typically requiring the growth of several microns of a graded Si1-xGex layer, followed by a buffer layer. In this work, we have used ion implantation of Ge followed by high- temperature annealing to form a relaxed substrate, eliminating the growth of graded, relaxed layers, and simplifying the fabrication process. Upon this film, a 1000 angstrom buffer layer of Si0.85Ge0.15 was grown. X-ray analysis indicates that the films formed by this method are 75% relaxed. This was followed by a 200 angstrom thick strained-Si layer. For comparison, unstrained Si epitaxial films and a 2000 angstrom thick film of Si0.85Ge0.15 (on unimplanted Si) followed by 200 angstrom of Si were used. A typical self-aligned MOS process with modifications to achieve low-thermal budget was used to fabricate NMOSFETs with gate lengths ranging from 10 micrometer to 0.8 micrometer. Strained-Si devices show a 17.5% higher peak linear gm than control devices as a result of higher electron mobility in the strained-Si channel.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Soji John, Samit K. Ray, Sandeep K. Oswal, and Sanjay K. Banerjee "Strained Si NMOSFET on relaxed Si1-xGex formed by ion implantation of Ge", Proc. SPIE 3212, Microelectronic Device Technology, (27 August 1997); https://doi.org/10.1117/12.284584
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