Phase-change memory now requires less current
Phase-change memory is a type of fast, cheap, and non-volatile memory whose only drawback is its high programming current requirement, which limits miniaturization potential and maximum density. However, Leti researchers have obtained promising results from a new “confined structure” phase-change memory architecture that allows for 50 nm chips—substantially smaller than the 300 nm currently available with standard plug architecture.
This breakthrough was achieved by combining e-beam lithography with an atomic thin film deposition process developed by ASM International N.V. and a special chemical-mechanical polishing process. The confined structure architecture uses the phase-change material GeSbTe, and will be developed further to be compatible with tomorrow’s sub-45 nm technology nodes.
3D packaging: Leti unveils a test pattern library
Leti now offers partner businesses and universities an expansive library of 3D test patterns, built from the laboratory’s years of research on 3D stacking technology. The library can be used to test the performance of various interconnections and check compliance with specifications—from the very outset.
The patterns can be used to test through-silicon vias (TSVs), or vertical connections through stacked chips, as well as the interconnections between different components. The first organizations to use the library are the European Organization for Nuclear Research and EADS subsidiary Cassidian. For other research laboratories, Leti plans to offer test patterns that can be easily embedded on customers’ wafers.
Dr. Yves Bréchet appointed France’s High Commissioner for Atomic and Alternative Energy
Dr. Yves Bréchet, a Grenoble Institute of Technology-Phelma professor and researcher at the French Materials and Process Engineering Laboratory (SIMaP), has been appointed France’s High Commissioner for Atomic and Alternative Energy by the country’s Cabinet of Ministers. This appointment follows a recommendation by the French Minister of Research and Higher Education, Geneviève Fioraso.
With this appointment Dr. Bréchet becomes the official Science and Technology Advisor to the President of the French Atomic and Alternative Energy Agency and to the French government for issues covered by the Agency. Dr. Bréchet also heads the Academic Board of the French National Institute of Nuclear Science (INSTN), ensuring the scientific merit of the Institute’s work. Dr. Bréchet has also been designated the 2012–2013 Chair of Technological Innovation at the prestigious Collège de France.
Yes, topological insulators do exist
Do topological insulators—substances that act like insulators on the inside but whose surface contains conducting states—really exist? It would appear so based on experiments conducted on quantum wells just a few nanometers thick, but the findings are difficult to apply to three-dimensional objects. However, now a CNRS-Leti research team has discovered these surprising properties on a sample they created that is several tens of nanometers thick.
This research will be developed further under a new project called Semitopo, to be funded by the French National Research Agency. Semitopo will focus on the characterization and optimization of these first “made in Grenoble” topological insulators; the Synchrotron will be used to take measurements.
The topological insulators are made of constrained layers of mercury telluride deposited on cadmium telluride substrates. The first challenge was to make the insulators; Leti had to draw on its 30 years’ experience in molecular beam epitaxy, a process developed—and continually being improved—for Sofradir infrared imaging systems. Scientists at Institut Néel then characterized the insulators using transport measurements.
The study of topical insulators also has applications in applied research. Since they are able to carry a spin current without a magnetic effect, they can be used to make spintronics and, eventually, quantum computers.
Leti unveils a 10 Gb/s integrated transmitter-on-silicon
Leti and III-V Lab have marked a major step forward in silicon photonics by combining onto a single chip a hybrid laser (III-V materials and silicon) with 9-nm wavelength tunability and a silicon modulator. Conventionally, the laser sources for photonic components are fabricated separately and transferred onto the substrate, which complicates the process and results in higher costs.
This next-generation transmitter was developed under the EU Helios project in association with Belgian and British researchers. It has numerous applications in telecoms, such FTTH networks and data transfer among and within data centers. The project team is now looking to achieve higher bandwidths, like 25 Gb/s—or even 40 Gb/s.
Leti set to make greater use of ESRF’s D2AM beamline
Leti has recently entered into a partnership agreement with ESRF to increase its usage of the D2AM beamline. The two research centers have agreed to share time on the beamline over the next five years in order to facilitate and speed its usage (under two months). Young scientists supervised by both centers will carry out joint research projects on the beamline, and the centers have already applied for funding from the French National Research Agency to study silicides for fully-depleted silicon-on-insulator (FD-SOI) applications.
The D2AM beamline can be used for spectroscopy, diffraction, and diffusion, and perfectly rounds out Leti’s characterization capabilities. It can be used with very high-brilliance synchrotron sources with variable wavelengths. Leti scientists intend to use it to observe nanometric layers and buried objects, for example.
Hygrothermal aging of Nafion® membranes not observed during fuel-cell operation
There are many potential reasons behind the aging of the Nafion® membranes used in fuel cells. However, thanks to researchers from INAC, Liten, and ENSAM Paris, we now know that hygrothermal aging is not one of them. The researchers demonstrated that hygrothermal aging of the membranes does not occur during fuel-cell operation. In fact, the researchers found that a membrane previously aged under ex situ conditions could be completely rejuvenated after 800 hours’ fuel-cell operation.
Hygrothermal aging is caused by sulfonic acid end-group condensation. But all fuel cells produce water, which, according to the researchers’ observations, virtually eliminates the condensation. The researchers will now have to find a new culprit!
CEA France’s third-leading patent filer in 2011
The CEA was France’s third-leading patent filer in 2011, coming in just behind PSA Peugeot Citroën and Safran, and way ahead of other research centers like CNRS (6th) and IFP (11th). With 545 patents filed, the CEA also came in ahead of corporations like L’Oréal, EADS, Thales, Valeo, and Renault, all international leaders in their fields.
Patents are one of the cornerstones of the CEA’s technology transfer policy. Without the protection a patent provides, it would be difficult to transfer a new technology to industry without putting it at risk. Also in 2011, CEA and MINATEC labs tallied up more than 2,000 collaborative research agreements that brought in some €800 million in revenue. Also worth noting: the CEA is France’s top filer of patents via the Patent Cooperation Treaty procedure, which makes it easier to secure patent protection in several countries simultaneously.
The ideal commutation system?
Researchers from IMEP-LAHC and Leti—with the help of a Brown University scientist—recently made an exciting chance discovery: the Z2-FET, a PIN-MOS diode that offers a grid voltage variation of just 1 mV for switching, increasing the current by 8 decades.
The team was working to develop new tunneling SOI transistors when they made the discovery. While exploring new ways to optimize polarization voltage, they stumbled upon the new—and perhaps ideal—commutation system.
On a Z2-FET, negative voltage is applied to the grid and positive voltage is applied to the substrate. This creates two potential barriers. When the voltage applied to the grid is increased, the first barrier lets electrons through; these electrons then cross the second barrier. What is even more impressive is that all of this occurs with a grid voltage variation of just 1 mV. For comparison, MOSFET transistors require 60 mV to increase the current by 1 decade.
The new system will be presented at the IEEE’s VLSI-TSA international symposium in April, and two patent applications have already been filed. Several manufacturers have expressed interest in the system, which is compatible with CMOS-on-SOI technology and can be miniaturized down to just 50 nm in length.
However, what is most exciting is the system’s extremely low power consumption, which will open the door to a host of new opportunities. The researchers are focused primarily on memory applications for the moment, but the Z²-FET could also be used in low-power fast-switching logic circuits.