(December 13, 2010) — At the 2010 IEEE IEDM conference (12/6/10, San Francisco), Semiconductor Research Corporation (SRC) and researchers from Waseda University in Tokyo announced the development of the process and materials for precisely controlling both the amount and the position of channel dopants. The researchers say this advance should help extend the manufacturability of semiconductors beyond conventional doped-channel device technologies. The result is projected to enable near atomic-scale devices and single-dopant devices.

The paper, #26.5 ("Reliable single atom doping and discrete dopant effects on transistor performance") was co-authored by NTT Basic Research Laboratories and Tohoku University, and was presented by Waseda University. According to Dan Herr, SRC director of Nanomanufacturing Sciences, "Deterministic doping, per our single-ion implantation, is a key step for the extensibility of existing doped-channel CMOS devices at 16nm and beyond."

According to SRC, the findings demonstrate the impact of a very small number of dopant atoms on device performance, making the assumption of uniform dopant distribution incorrect. The naturally occurring non-uniform distribution causes significant variability in transistor characteristics, threatening further semiconductor miniaturization.

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SRC’s EVP, Steve Hillenius, told ElectroIQ’s Debra Vogler, senior technical editor, that the research allows for a tool that enables precise doping profiles — literally putting individual atoms in a transistor channel. "As an analytical tool, it’s very useful in being able to make precise doping profiles and then studying the effects in moving one atom from one position to another in comparison with devices made with one distribution of dopants vs. another," said Hillenius (Figure). "Non-uniform doping across the channel is always a useful tool or knob to turn when designing transistors." He explained that by getting down to single ion doping, the researchers were able to do an extensive study of quantifying the effects on device characteristics depending on whether dopants were closer to the source, and then when they were closer to the drain. The researchers reported that the sub-threshold current is sensitive to the individual dopant location, and the sub-threshold current is always larger when the dopants are located at the drain side rather than at the source side.

Figure. Evaluation of electrical transport in FETS with discrete dopants.

"This research enables a real understanding of what the impacts are of process variations and very precise processing that will allow these effects to be done on a large scale," Hillenius told ElectroIQ. By doing so, the researchers are enabling device designers of processes for mass production to target a certain dopant profile to get the maximum performance out of a transistor.

Regarding its collaboration activities, Hillenius said that SRC is very happy with its collaboration and the high quality of research coming out of Waseda as well as with other universities around the world. "It’s only been the last few years that we’ve been funding research in Japan," said Hillenius. “This kind of research, in conjunction with the interests of our Japanese members, allow the university research and the students coming out to be very well suited to working in SRC member companies.”

With its Energy Research Initiative, SRC is also expanding research activities in the areas of energy and renewable energy applications. "We have a lot of hope of expanding such research in Japan," said Hillenius. The majority of members of this initiative are from countries other than the U.S. — only two U.S. companies are involved. 

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