Nav: Home

Managing stress helps transistor performance

May 16, 2017

WASHINGTON, D.C., May 16, 2017 -- Tensile mechanical stress can have a useful effect for some transistors, where the resulting atomic strain allows its current-carrying electron-hole pairs better mobility. However, when that stress is applied to the whole device, as is a popular approach via use of what's called contact etching stop layers (CESLs), the drift region adjacent to the stretched channel is compressed and results in reduced performance.

A research team in China have developed a new CESL method that introduces tensile stress into both the channel and the drift region, improving overall performance by offering low drift resistance, high cut-off frequency and desirable breakdown characteristics. Their work is described in an article appearing this week in the journal AIP Advances, from AIP Publishing.

The team of researchers became interested in the method because of work done on strained silicon techniques. During research on strained meta-oxide semiconductor field effect transistors (MOSFETs), researchers saw that the stress in the source/drain region was inverse to the channel region stress. Based on these observations, they began to study how they might use this phenomenon in a way that could enhance performance.

This new research focused on partial silicon-on-insulator (PSOI) devices that introduce tensile stress into both the channel and the drift region using the CESLs. Simulation results also showed that the PSOI device offers better frequency performance and driving capability than unstrained devices.

"The most difficult thing for us was to find a low cost, CMOS-compatible method for applying mechanical stress," said Xiangzhan Wang, from the University of Electronic Science and Technology of China. "During the manufacturing process, the wafer bends as the stress film (Si3N4) grows, which creates a problem in holding the wafer in process equipment."

The experiment results, however, increased confidence that the new strain technique could not only be applied to small devices, but also to rather large devices to yield performance improvement. With the results, even the research team was surprised at the level of improvement it provided to their simulations.

"In our simulation, the fully tensile strained PSOI n-type LDMOSFET showed a 20-30 percent driving current improvement over normal Si LDMOSFET," Wang said. "But when we used this strain method with a commercial Si LDMOS product, the driving current doubled yielding a current increase of more than 100 percent, which was quite surprising for us."

While this work has contributed to understanding of the strained Si mechanisms, there is still more to improve and understand.

"The next research directions for the team are to optimize the fabrication process for these devices in order to obtain better stability and to try applying the same method to a nonsymmetrical device such as a tunnel FET," Wang said.
-end-
The article, "Fully tensile strained partial silicon-on-insulator n-type lateral-double-diffused metal-oxide-semiconductor field effect transistor using localized contact etching stop layers," is authored by Xiangzhan Wang, Changgui Tan, Xi Zou, Yi Zhang, Jianhua Pan, and Yang Liu. The article appears in the journal AIP Advances on May 16, 2017 [DOI: 10.1063/1.4983214]. It can be accessed at: http://aip.scitation.org/doi/full/10.1063/1.4983214

ABOUT THE JOURNAL

AIP Advances is a fully open access, online-only, peer-reviewed journal. It covers all areas of applied physical sciences. With its advanced web 2.0 functionality, the journal puts relevant content and discussion tools in the hands of the community to shape the direction of the physical sciences. See: http://aipadvances.aip.org.

American Institute of Physics

Related Stress Articles:

Stress in the powerhouse of the cell
University of Freiburg researchers discover a new principle -- how cells protect themselves from mitochondrial defects.
Measuring stress around cells
Tissues and organs in the human body are shaped through forces generated by cells, that push and pull, to ''sculpt'' biological structures.
Cellular stress at the movies
For the first time, biological imaging experts have used a custom fluorescence microscope and a novel antibody tagging tool to watch living cells undergoing stress.
Maternal stress at conception linked to children's stress response at age 11
A new study published in the Journal of Developmental Origins of Health and Disease finds that mothers' stress levels at the moment they conceive their children are linked to the way children respond to life challenges at age 11.
A new way to see stress -- using supercomputers
Supercomputer simulations show that at the atomic level, material stress doesn't behave symmetrically.
Beware of evening stress
Stressful events in the evening release less of the body's stress hormones than those that happen in the morning, suggesting possible vulnerability to stress in the evening.
How plants cope with stress
With climate change comes drought, and with drought comes higher salt concentrations in the soil.
Gene which decreases risk of social network-related stress, increases finance-related stress risk
Researchers have discovered that the same gene which increases your risk of depression following financial stress as you grow older also reduces your chance of depression associated with friendship and relationships stresses when young- your social network.
Innate stress
A team of researchers from the Higher School of Economics and the RAS Vavilov Institute of General Genetics has been able to statistically monitor the impact of the monoamine oxidase A gene (MAOA) on the subjective evaluation of well-being among men.
Is a stress shot on the horizon?
Rats immunized weekly for three weeks with beneficial bacteria showed increased levels of anti-inflammatory proteins in the brain, more resilience to the physical effects of stress, and less anxiety-like behavior.
More Stress News and Stress Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.