Portland, Ore. In search of a single-chip cell phone, researchers worldwide are seeking alternatives to the many discrete front-end surface-acoustic-wave filters (SAWs) and other tunable radio frequency (RF) components required by today's communications devices.
Now the European Union is proposing to use nanostructured ferroelectric films to integrate tunable microwave devices onto silicon-based microwave communications devices. The EU's Nanostar project (www.nanostar-eu.com) is a three-year effort aimed at bringing the electronics industry one step closer to a single-chip cell phone.
"The Nanostar project will engineer materials with radically new dielectric properties that exploit new physical effects in nanostructured ferroelectrics," said professor Spartak Gevorgian of Chalmers University of Technology in Gothenburg, Sweden, who is the coordinator of the project. "Devices based on these films will offer a substantial reduction of cost, size and power consumption for portable, handheld devices such as mobile phones, PDAs and laptops. They can also be applied in adaptable/reconfigurable microwave systems that use large numbers of tunable components, such as large phased-array antennas and tunable metamaterials."
Participating in the $5 million (4.1 million euro) project are researchers from Chalmers University of Technology; Philips Electronics Nederland (Eindhoven, Netherlands); Ericsson (Mölndal, Sweden); Temex Filters, (Sophia Antipolis, France); the Swiss Federal Institute of Technology (Lausanne, Switzerland); and Electrotechnical University (St. Petersburg, Russia).
SAW devices have replaced bulk ceramic and quartz as microwave filters, correlators and modulators. But since they are not fabricated on silicon, Philips and others have turned to bulk acoustic-wave-devices that can be fabricated on silicon.
But the Nanostar program aims to demonstrate that ferroelectric films can offer lower cost and power as well as new performance capabilities.
Ferroelectric films are already being integrated into silicon-based memory chips as the capacitors for bit cells, but they can also be used in an analog mode as voltage-controlled capacitors (varactors) that are useful in tunable microwave components. However, the Nanostar program aims to exploit the other properties of ferroelectrics to create unique devices that someday could enable a single-chip cell phone.
"Our demonstrations will be developed for microwave communications applications, but we will also demonstrate potentially useful optoelectronic and sensing devices, such as tunable thin-film bulk acoustic resonators, which have no analogue in today's electronics industry," said Gevorgian.
To that end, the Nanostar project will concentrate its efforts on developing ferroelectric materials that use complex metal-oxide dielectrics, such as barium and strontium titanate, which have very high magnetic permittivity that is independent of electrical field strength. Usually, high permittivity reduces electric field strength. The Nanostar researchers aim to harness this unusual property of ferroelectrics to fabricate unique integrated components by focusing on nanoscale patterning of ferroelectric films.
The program also aims to use patterning to solve the engineering problems associated with transforming experimental ferroelectric devices into competitive commercial components.