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Sunday, September 6, 2015

#330 Porosity in semiconductor technology

The terms porosity refers to the material which includes significant volume of pores (voids) in its structure.  At the first glance, porosity does not seem to be a desired feature of materials used to make semiconductor devices.  The following two examples contradict this perceived notion and demonstrate how material’s porosity can be exploited in semiconductor device engineering.  


First example is concerned with low-k dielectrics used in multi-level metallization scheme in advance IC manufacturing. Here, nanopores (essentially air gaps)  included in the structure of an insulating dielectric lower its dielectric constant k and increase its ability to reduce capacitive coupling between adjacent metal lines.


Second example involves porous silicon (p-Si), i.e. silicon which includes large volume of pores in its structure.  With very little material remaining between the voids, silicon in porous form experiences pronounced geometrical confinement making it display quantum confinement effects. As a result, its fundamental physical characteristics are becoming very different from those displayed by the bulk Si. The most visible manifestation of the these differences is a wider energy gap of p-Si  which makes it emit visible red-orange light as opposed to invisible infra-red radiation generated by the narrower energy gap bulk Si. Also, very large surface to volume ratio of porous Si make bring about some innovative interesting applications for this “full of air” version of silicon.


Posted by Jerzy Ruzyllo at 02:22 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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