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Sunday, January 11, 2015

#317 "3.9" is an another number to remember.

Following on the "number to remember" theme, 3.9 is another number which is flat out remembered by those involved in semiconductor engineering.


The dielectric constant k of SiO2 is 3.9. What is special about this value is that it serves as a reference in defining what is a high-k dielectric and what is a low-k dielectric. In the broadly commonly accepted terminology the dielectrics featuring k>3.9 are referred to as high-k dielectrics and those featuring k < 3.9 as low-k dielectrics.
The high-k dielectrics are needed wherever strong capacitive coupling between two conductors separated by  the dielectric is needed. The most obvious example is a MOS gate stack where, since 45 nm technology generation, gate dielectrics featuring high-k are used so that adequate gate capacitance is maintined at the physically thicker dielectric.
The  demand for the low-k dielectrics is coming from the multi-level interconnect technology where the capacitive coupling between two interconnect lines is highly undesirable, and hence,  interlayer dielectrics featuring as low as possible dielectric constant must be used.


In the light of the key role both high-k and low-k dielectrics are playing, a "3.9" has become a number of great relevance in the advanced semiconductor engineering.  I found it interesting that some 15-20 years ago the issue of high- and low-k was not of much relevance in semiconductor device engineering  as  SiO2 with its  k= 3.9 was used in both MOS gates and multilevel metallization applications.


Posted by Jerzy Ruzyllo at 04:50 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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