source :The International Technology Roadmap for Semiconductors (ITRS) continues to provide the most up to date view into the semiconductor industries technology requirements and potential solutions for those requirements.(1) As noted several years ago by Dan Hutcheson, the feature sizes for today's devices and interconnects placed the integrated circuit well into the world of Nanotechnology.(2) As ITRS states, the semiconductor industry will squeeze all the performance out of existing CMOS transistor technology in an effort to extend it for as long as possible. The ITRS teams are also looking into the future beyond CMOS. Nano Science and Technology pay critical roles in both CMOS extension and in "Beyond CMOS". The 2007 ITRS will have sections on both Emerging Research Materials and Emerging Research Devices. These sections describe potential new device technology and some of the materials that are being researched for use in these devices. In addition, the ITRS Metrology Roadmap has a section on measurement needs and methods for Emerging Research Materials and Devices.
The industry search for a new device to replace or augment the transistor requires significant amounts of research and development in universities, national laboratories, and industry itself. Some of the concepts being explored include using spin transport instead of charge transport, molecular electronics where changes in molecular configuration govern charge transport, excitonic devices. New materials such as graphene, carbon nanotubes, semiconductor nanowires, metal oxides, and quantum dots are under consideration as the materials that would be used to fabricate the device.
Underpinning both CMOS extension and beyond CMOS devices are new phenomena that manifest themselves only when materials are fabricated into nano-scale dimensions. As one can glean from experienced semiconductor technologists, shrinking dimensions has always brought on both new performance and new problems. Everything from materials strength to quantum confinement impact properties at nanoscale dimensions. In addition, the measurement process itself is subject to new physics at these length scales.
There are countless challenges facing characterization and metrology of nano-scale materials and devices. All areas from microscopy to spectroscopy must be advanced at a more rapid pace. Although improvements in microscopy, such as aberration corrected lens systems, have continued at unprecedented rates, electron microscopy of soft materials such as graphene and molecular electronics remain exceedingly difficult. The combination of experiment and modeling are required to accelerate progress. For example, simulation of TEM images both improve image interpretation and point to optimum imaging conditions. Theory is also necessary for interpretation of electron energy loss spectra. The ITRS is calling for measurements such as carrier spin with presently unachievable spatial localization of the information. Scanned probe methods including BEEM (ballistic electron emission microscopy)are providing new insights into materials properties such as spin transport. Recent work shows that nanoscale phenomena on optical properties such as quantum confinement provide a means of extending optical methods to smaller dimensions.(3) Measurements the detect defects in nanostructures such as graphene and correlate them to resultant properties are very important. Recent work at the National Institute of Standards and Technology showed how scanning tunneling microscopy can observed such phenomena.(4)
Another set of measurement needs is for uniformity of properties of nanoscale materials. For example, what is the average and range of the dimensions of an assembly of nanodots? Numerous properties need to be characterized for such arrays. How does one measure this uniformity at the precision required for volume manufacturing control? The semiconductor industry has faced these issue for many years.
So in December when the 2007 ITRS is released, the Emerging Research Materials, Emerging Research Devices, Metrology, and other sections of the ITRS will provide us with a very useful overview of how important the semiconductor industry finds Nano-Scale Science and Technology.
1. International Technology Roadmap for Semiconductors WEB-Site http://www.itrs.net
2. G. Dan Hutcheson. The first nanochips. Scientific American, pages 48-55, April 2004.