'Sandwich chips' combining the best of two technologies

Dec 18, 2012
Wafer with "Sandwich Chips". Credit: BH/Immerz

Two Leibniz institutes in Germany broke new technological ground and successfully combined their – up to now separate – technology worlds. Due to their high performance the novel chips developed within the HiTeK project shall open up new applications.

Wolfgang Heinrich and Bernd Tillack are convinced of holding the key to faster and more powerful terahertz chips. The two scientists and their teams come from the Berlin-based Ferdinand-Braun-Institut (FBH) and from the IHP–Leibniz-Institut für innovative Mikroelektronik in Frankfurt/Oder – and thus from two different technology worlds. FBH is one of the leading institutes in developing III-V semiconductors, while IHP is specialized in silicon-based systems and circuits. Both Leibniz institutes joined forces within the HiTeK project to combine the advantages of silicon-based CMOS () circuits from the IHP with those of circuits from the FBH. The partners now accomplished an important step within the project by successfully integrating both circuits on a , with measurement results demonstrating their high performance. With the integration on one chip, new ambitious applications in the THz range are within reach such as high-resolution imaging systems for medical and security technology as well as ultra-broadband mobile communication applications.

For such applications high output powers along with faster computer processors are needed offering enhanced computer operation per second. In order to achieve this, circuits on the chips have to become smaller—the key reason which boosts miniaturization in . If the frequency range around 100 and beyond is to be covered, however, the in the CMOS switching circuits decreases significantly. Accordingly, the available output power of the chips declines, which implies that the capability to generate sufficiently strong signals to establish a radio link and to detect material defects becomes insufficient. To find a solution for this problem, IHP conducts research on bipolar CMOS based on silicon-germanium enhancing the breakdown voltages at high speed compared to pure CMOS. By combining a standard CMOS circuit with a second indium-phosphide circuit promises further improvement. Both circuits are realized "sandwich-like" on top of each other. 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 allow to keep benefiting from the high level of production routine and integration of CMOS circuits – particularly regarding the fact that 95 % of all digital and analogue-digital circuits base 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 gigahertz. Precision work was also highly demanded to adjust the circuits precisely to each other with an accuracy of less than 10 micrometers. 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 now to further stabilize the process and to optimize the circuits. A follow-up project has already been granted. This way, the potential of the hybrid chips shall be exploited fully to reach the borders of what is feasible – thus setting the stage for the novel sandwich to be integrated in sophisticated applications soon.

Explore further: X-ray detector on plastic delivers medical imaging performance

add to favorites email to friend print save as pdf

Related Stories

Graphene mixer can speed up future electronics

Jan 03, 2012

Researchers at Chalmers University of Technology (Sweden) have for the first time demonstrated a novel subharmonic graphene FET mixer at microwave frequencies. The mixer provides new opportunities in future ...

45-nanometer chips for ultra-fast WiFi

Jul 29, 2009

(PhysOrg.com) -- Powerful new radio technologies that promise blisteringly fast WiFi have been given a boost by a team of European researchers’ cutting-edge work on miniscule microchips.

Recommended for you

Jacket works like a mobile phone

1 hour ago

A fire is raging in a large building and the fire leader is sending a message to all firefighters at the scene. But they don't need a mobile phone – they simply check their jacket sleeves and read the message ...

Is nuclear power the only way to avoid geoengineering?

1 hour ago

"I think one can argue that if we were to follow a strong nuclear energy pathway—as well as doing everything else that we can—then we can solve the climate problem without doing geoengineering." So says Tom Wigley, one ...

UN study: Cellphones can improve literacy

2 hours ago

A study by the U.N. education agency says cellphones are getting more and more people to read in countries where books are rare and illiteracy is high.

User comments : 0

More news stories

Jacket works like a mobile phone

A fire is raging in a large building and the fire leader is sending a message to all firefighters at the scene. But they don't need a mobile phone – they simply check their jacket sleeves and read the message ...

Is nuclear power the only way to avoid geoengineering?

"I think one can argue that if we were to follow a strong nuclear energy pathway—as well as doing everything else that we can—then we can solve the climate problem without doing geoengineering." So says Tom Wigley, one ...