Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Electron trapping' may impact future microelectronics measurements

01.07.2008
Using an ultra-fast method of measuring how a transistor switches from the "off" to the "on" state, researchers at the National Institute of Standards and Technology (NIST) recently reported that they have uncovered an unusual phenomenon that may impact how manufacturers estimate the lifetime of future nanoscale electronics.

The transistor is one of the basic building blocks of modern electronics, and the life expectancy or reliability of a transistor is often projected based on the response to an accelerated stress condition. Changes in the transistor's threshold voltage (the point at which it switches on) are typically monitored during these lifetime projections.

The threshold voltage of certain types of transistors (p-type) is known to shift during accelerated stresses involving negative voltages and elevated temperatures, a characteristic known as "negative bias temperature instability" (NBTI). This threshold voltage shift recovers to varying degrees once the stress has ended. This "recovery" makes the task of measuring the threshold voltage shift very challenging and greatly complicates the prediction of a transistor's lifetime.

As semiconductor devices reach nanoscale (billionth of a meter) dimensions, measuring this device reliability accurately becomes more important because of new materials, new structures, higher operating temperatures and quantum mechanical effects. Many NBTI studies show that the accuracy of the measured threshold voltage shift (and consequent accuracy of the lifetime prediction) depends strongly on how quickly the threshold voltage can be measured after the stress is finished. So, NIST engineers began making threshold voltage measurements at very fast speeds, leaving as little as two microsceconds (millionths of a second) between measurements instead of the traditional half-second interval. What they observed was surprising.

"We found that NBTI recovery not only returned the threshold voltage to its pre-stressed state but briefly passed this mark and temporarily allowed the transistor to behave better than the pre-stressed state," says Jason Campbell, a member of the NIST team (that includes Kin Cheung and John Suehle) who presented this finding at the recent Symposium on VLSI Technology in Hawaii. The NBTI effect generally is believed to result from the buildup of positive charges, he explained, but the new observations at NIST indicate the presence of negative charge as well. NIST's ultra-fast and ultra-sensitive measurements revealed that during recovery, the positive charges dissipated faster than the electrons, giving the system a momentary negative charge and heightened conductivity.

To date, Campbell says, transistor manufacturers only consider the accumulation of positive charges to predict the longevity of their microelectronics devices. "But as these systems get smaller and smaller, the electron trapping phenomenon we observed will need to be considered as well to ensure that transistor lifetime predictions stay accurate," he says. "Our research will now focus on developing and refining the ability to measure that impact."

Michael E. Newman | EurekAlert!
Further information:
http://www.nist.gov

More articles from Power and Electrical Engineering:

nachricht Multicrystalline Silicon Solar Cell with 21.9 % Efficiency: Fraunhofer ISE Again Holds World Record
20.02.2017 | Fraunhofer-Institut für Solare Energiesysteme ISE

nachricht Six-legged robots faster than nature-inspired gait
17.02.2017 | Ecole Polytechnique Fédérale de Lausanne

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>