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Sunday, April 13, 2014

#284 Silicon and copper

Copper is not a friend of silicon. In fact, it should be considered one of its worst enemies. Unfortunately, copper contamination is fairly common in silicon processing. Copper can contaminate the surface during wet cleaning operations and penetrate beneath the surface as a component of the polishing slurries during wafer manufacturing.


The problem is that copper features extremely high diffusivity and high solubility in Si. With any thermal step, copper will spread around Si lattice almost instantaneously. During thermal processes, combined with strain in the lattice and/or concentration gradient, copper will precipitate in silicon, decorate other defects and overall act as a major killer of the carrier lifetime, and hence, ruin the performance of any device. Furthermore, if allowed into the gate oxide on Si surface, copper will thoroughly destroy dielectric integrity of such oxide.


Considering all of the above it is no wonder that introduction of copper as interconnect metal replacing aluminum in advanced silicon integrated circuits was delayed by the industry as much as possible. Eventually, it did happen but only because copper as interconnect line never comes in contact with Si from which it is carefully separated by barrier layers as well as interlayer insulators.

Posted by Jerzy Ruzyllo at 07:58 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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