SemiSerious

Perhaps the DaVinci Code and the legend of the Priory of Sion is no longer topical, but Sion’s namesake compound – SiON or silicon oxynitride – is extremely relevant in the semiconductor industry. Unlike Sion though, SiON at 65nm is no hoax – pushing exotic high-K materials out to 45nm for high performance logic processes and possibly further.

When Intel was pre-occupied with clock speed and the gigahertz race, their fabs pushed gate dielectrics very hard. Unfortunately, leakage through those ever-thinner dielectrics sucked a lot of power even when the logic gates were idle. Power consumption concerns brought an end to thinning the gate dielectric at 90nm for Intel. Their 65nm process uses the same physical dimension of 1.2nm.  The strategy for the entire industry to increase transistor performance for the 65nm generation is to optimize the nitridation processes and increase the nitrogen content in the gate dielectric film. Higher nitrogen content increases the dielectric content of the film which has the same effect as a thinner film of lower K value. The effective oxide thickness or EOT allows different materials to be easily compared by referring them to the pure oxide of silicon , SiO2.

All this begs the question, “Wouldn’t it be great if you could actually look deeply into these ultra-thin films to see how much nitrogen they contain and where it is localized?”

Believe it or not, there is now a way study of state-of-the-art gate dielectrics on real world production parts.  A new report from Semiconductor Insights reveals the strategy for decreasing EOT just as the industry reacts to announcements by both Intel and the IBM alliance that their respective 45nm transistors will incorporate hafnium-based dielectrics along with metal gates. SI’s landmark new report provides details of the changes in nitrogen content through the dielectric from channel to gate. High performance AMD, Intel and UMC processes are compared along with the low stand-by power TI process.

Along with standard high resolution lattice fringe TEM imaging that provides the most accurate measurement of film thickness, electron energy loss spectroscopy or EELS data are analyzed to create an understanding of the nitridation process and its effect on device performance.

Hafnium-based dielectric films promise a lot and offer a great opportunity for analysis when they arrive later next year. Fortunately, the technology needed to study those devices is available now. For now, there is a lot to learn from the optimized SiON films at 65nm. But if you just must know more about hafnium oxide high-K in production, Samsung uses it in their 80nm DRAM capacitor.

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