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Sunday, March 30, 2014

#282 Silicon and carbon

In addition to hydrogen (see below) carbon is another element which plays a special role in silicon device technology. Unlike in the case of hydrogen, however, the effect of carbon in silicon on material and device characteristics is unambiguously deleterious.


Once allowed into Si crystal, carbon, in contrast to hydrogen, cannot be removed from Si structure where its harmful role is triggered by the high temperature processes employed during device manufacturing. But what the mechanisms that allow carbon penetration of silicon?  For starters, carbon impurities end up in single crystal Si as a result of crystal growth process. If not contained within acceptable limits, carbon will lead to the formation of swirl defects which may be transformed into precipitates and stacking faults during wafer exposure to high-temperature. Furthermore, during the device processing, particularly during dry etch operations, carbon involved in etch chemistries can get “implanted” into a very shallow near surface region of Si substrate. Once there, it can cause all sorts of harms during subsequent high-temperature processes such as thermal oxidation or epitaxial deposition.


Yet another story is a control of carbon contamination of Si surfaces with carbon compounds resulting from resist stripping as well as interactions with hydrocarbons from the ambient air. Prevention of carbon penetration into Si lattice through very thorough cleaning of Si surface every step of the way is a key to the successful control of potentially very harmful impact of carbon contamination of Si surfaces.

In the light of all of the above it is interesting to take note of the other side of Si-C interactions. This other side is that the homogenous, stoichiometric bonding between Si and C forms silicon carbide (SiC) which is an excellent semiconductor. The point is to see a fine line between carbon acting as a major impurity in silicon and the same carbon being an integral part of silicon compound featuring very attractive characteristics.

Posted by Jerzy Ruzyllo at 11:48 AM | 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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