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news digest ♦ Telecoms


compared to pure CMOS. By combining a standard CMOS circuit with a second InP circuit promised further improvement.


Both circuits are realised in a “sandwich-like” structure and lie one on top of another. Where the traditional silicon-based CMOS technology reaches its limits, this novel material combination delivers the desired properties; high output powers at high frequencies. The sandwich chips enable a high level of production and integration of CMOS circuits - particularly regarding the fact that 95 percent of all digital and analogue-digital circuits are based on this technology.


“It was particularly challenging to make both technologies compatible at the interfaces”, underlines Wolfgang Heinrich from the FBH. To achieve this, the whole development environment of both processes as, for example, the software for the circuit layout had to be merged in a first step.


Subsequently, both layers had to be dimensioned so that they reach the essential good transmission properties for frequencies around 200 GHz. Precision work was also highly demanded to adjust the circuits precisely to each other with an accuracy of less than 10µm.


Heinrich is especially proud of the friction-less cooperation, “We managed to align both technology worlds so smoothly that the circuits deliver fully the specified high-frequency performance. This also demonstrates what added value can be created by bundling the competencies of two institutes like IHP and FBH”.


The next steps are to further stabilise the process and to optimise the circuits. A follow-up project has already been granted. In this way, the potential of the hybrid chips will be exploited fully to reach the borders of what is feasible. This will set the stage for the novel sandwich circuits to be integrated in sophisticated applications in the near future.


Terabit interconnect project combines III-Vs with silicon


The three year project announced by imec, will combine III-V high speed VCSELs with various silicon components to allow new functionalities such as wavelength multiplexing


MIRAGE, a new EU FP7 project, was recently launched with the goal to develop next-generation optical interconnect technology for terabit data links.


The project that focuses on optical rack-to-rack and board-to-board interconnects is scheduled to run for three years and brings together seven leading academic and industrial partners in the optical value chain.


Along with imec, the project participants are the National Technical University of Athens (Greece), Austriamicrosystems AG (Austria), OptoScribe Ltd. (UK), Technische Universität München (Germany), Aristotle University of Thessaloniki (Greece) and AMO GmbH (Germany).


Today the internet is morphing into a content-centric network with billions of users demanding ubiquitous, instant access to vast amounts of data. In this new networking paradigm, the hot spots are the data centres, where the bulk of the information is residing.


These data centres may consist of hundreds or even thousands of servers interconnected with each other. The content providers are in a constant race to increase this interconnection speed to improve the delivery of the data to the end user.


It is MIRAGE’s ambition to increase the optical interconnect speed, which currently tops at around 140Gb/s per link, and bring it to the terabit realm. To do so, the program will tackle the issues that still have to be solved to develop technology suitable for commercial adoption.


The project will look into a number of things. These include high speed III-V VCSELs, low-energy electronic drivers and a flexible motherboard technology that allow new functionalities such as wavelength multiplexing. MIRAGE will also explore multi-level modulation and multicore fibre coupling, and ways to introduce new degrees of


130 www.compoundsemiconductor.net January/February 2013


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