Sematech goes back to the future with germanium
Sematech, the collaborative semiconductor research and development partnership, has launched a project to investigate alternative materials for MOSFET channels, the critical pathways in silicon-based transistors.
The project will focus on germanium and SiGe primarily, while III-V compounds could feature in the longer-term.
Sematech's front-end processes (FEP) division will be at the forefront of the investigation, and will aim to develop process technology that increases channel mobility beyond silicon's physical limits without compromising on reliability.
FEP associate director Larry Larson said: "SiGe and germanium are currently the most promising materials for replacing silicon in planar channels in CMOS manufacturing." Larson described the initiative as a major new effort that could have far-reaching implications for the semiconductor industry.
Freescale's Hsing-Huang Tseng will manage the FEP's new program. "Continued CMOS scaling means we need to find new materials to replace silicon in these functions," he explained. "Germanium, SiGe and potentially III-V compounds could provide even bigger benefits for mobility enhancement."
Freescale already has plans to develop a GaAs-based MOSFET for commercial deployment, which it announced details of recently (see related story).
Before its rival became the all-conquering semiconductor material, germanium was a serious contender for commercial development, and the two elements share many basic properties. Germanium was largely discarded because of difficult integration issues, however.
Some of the studies of germanium that were carried out half a century ago are now proving to be a valuable resource, acknowledged Larson: "We're going back to publications from 1954 to obtain basic information on germanium."
Sematech launched its initiative in a workshop last December, at which a handful of material combinations were identified and referred to participating universities for long-term investigation.
The organization's FEP director, Raj Jammy, said: "Now that silicon device dimensions are approaching practical physical limits and involve increasingly complex processing techniques, alternate channels are becoming an attractive option for the first time."
Initial studies will focus on areas including the most promising variations of SiGe for low defect-density and performance enhancement, developing and characterizing SiGe and germanium source and drain junctions, and finding a suitable interface between a germanium channel and the high-k dielectric material used in the gate stack.
