Intel granted patent for Germanium Nanowire Transistors
Submitted as a patent application in April of 2010, the company first discussed a related invention at the 2010 International Electron Devices Meeting. Intel disclosed that it had developed P-channel transistors made from germanium, which the company said could be combined with complementary III-V N-channel transistors to form a suitable CMOS architecture. The focus on germanium is largely due to the fact that it is more mobile than silicon.
The patent itself reveals the use of a “germanium nanowire channel and the SiGe anchoring regions [that] are formed simultaneously through preferential Si oxidation of epitaxial Silicon Germanium epi layer.” Intel leverages a silicon fin as a “template” to align germanium nanowires on a chip while silicon-germanium anchors are used to mount to a silicon substrate. Germanium is likely to become a much more critical material in chip manufacturing in the future, as such nanowires “provide better control of short channel effects such as sub threshold slop and drain induced barrier lowering,” the patent states.
The extensive use of germanium has been discussed by the semiconductor industry for more than a decade, while first sophisticated germanium processors were predicted 15 years ago to arrive in the 2007 – 2008 time frame (similarly, the first graphene processors are now forecast to become available around 2020 – 2025). The history even goes back to 1959, when Jack Kilby built a microchip with germanium, but it was Intel-co-founder Robert Noyce who chose silicon and overcame. Back then, germanium was found to be limited by greater current leakage. Over the past ten years, the interest in germanium as a transistor material has increased significantly and has resulted in developments such as IBM’s 500 GHz GPU.