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 Scientists create biodegradable, paper-based biobatteries
08.08.2018 | Binghamton University

nachricht Ricocheting radio waves monitor the tiniest movements in a room
07.08.2018 | Duke University

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: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

Im Focus: World record: Fastest 3-D tomographic images at BESSY II

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

'Building up' stretchable electronics to be as multipurpose as your smartphone

14.08.2018 | Information Technology

During HIV infection, antibody can block B cells from fighting pathogens

14.08.2018 | Life Sciences

First study on physical properties of giant cancer cells may inform new treatments

14.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>