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Sunday, March 1, 2015

#321 Atomic-scale and its intricacies

The atomic-scale technology opens new possibilities in semiconductor device engineering and this is great. But with a caveat, however. Problem is that electrons start behaving in a strange way in the extremely confined spaces. Whether it is in the heavily 2D confined planar channel in Ultra-Thin Body SOI or vertical “fin” acting as a channel, current carrying electrons are subject to interactions which they do not encounter in 3D, or bulk, materials and which result in the deterioration of device performance.



What is the threshold at which those undesired effects are coming to play? It depends on the electric field which is moving electrons, crystal structure of the material and most notably on the crystallographic orientation of the surfaces confining the space in which electrons are moving. It appears that at the thickness/width somewhere around 4-5nm electrons “discomfort” is becoming very noticeable.  It means that when the semiconductor is confined in one dimension to less than about 20 atoms across (becoming effectively a 2D material system) there is no room for electrons to drift across it in the unobstructed way. They start interacting with each other and encounter scattering events which cause significant reduction of their mobility, and hence, deterioration of current driving characteristics of the transistor.


The good news is that it does not mean the end of the story for the atomic-scale technology. It only means that the description of the electrons behavior in semiconductors using tools of the classical physics runs its course and we need to switch to the next gear and adopt the laws of the quantum physics to comprehend what is going on. In other words, we need to forget about the corpuscular nature of an electron and consider it as a wave. Simple, right?

Posted by Jerzy Ruzyllo at 05:26 PM | Semiconductors | Link is the personal blog of Jerzy Ruzyllo. With over 35 years of experience in academic research and teaching in the area of semiconductor engineering (currently holding position of a Distinguished Professor of Electrical Engineering and Professor of Materials Science and Engineering at Penn State University), he has a unique perspective on the developments in this progress driving technical domain and enjoys blogging about it.

With over 2000 terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today.

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