Finding the True Measure of Nanoscale 'Roughness'

Jun 16, 2005
Finding the True Measure of Nanoscale 'Roughness'

Straight edges, good. Wavy edges, bad. This simple description holds true whether you are painting the living room or manufacturing nanoscale circuit features.
In a technical paper* published in June, researchers at the National Institute of Standards and Technology (NIST) and SEMATECH describe an improved method for determining nanoscale "linewidth roughness," an important quality control factor in semiconductor fabrication. Their research shows that current industry measurement methods may be exaggerating roughness of the smoothest circuit features by 40 percent or more above true values.

Image: A colorized scanning electron microscope image shows the "waviness" or roughness of edges on reference lines made of silicon that are about 100 nanometers wide. Credit: B. Bunday, SEMATECH/K. Talbott, NIST

As circuit features shrink in size to below 50 nanometers, wavy or rough edges within semiconductor transistors may cause circuit current losses or may prevent the devices from reliably turning on and off with the same amount of voltage.

"With this type of measurement," says NIST's John Villarrubia, "besides the real roughness there is also a false roughness caused by measurement noise. Our method includes a correction to remove bias or systematic error from the measurement."

Random noise, by definition, causes the measured value to be sometimes higher, sometimes lower than the true value, and can be minimized by simply averaging an adequate number of measurements. Systematic error, however, is consistently above or consistently below the true value due to some quirk of the measurement method.

The noise in nanoscale scanning electron microscope (SEM) images consistently adds extra roughness, says Villarrubia. The NIST/SEMATECH method involves taking two or more images at exactly the same location on a circuit feature, comparing the values, and subtracting the false roughness caused by measurement noise. SEM manufacturers should be able to incorporate the new method into their proprietary software for automated linewidth roughness measurements.

* J.S. Villarrubia and B.D. Bunday, Unbiased Estimation of Linewidth Roughness, Proceedings of SPIE 5752 (2005) pp. 480-488.

Source: NIST

Explore further: Spiraling laser pulses could change the nature of graphene

Related Stories

What are extrasolar planets?

May 25, 2015

For countless generations, human beings have looked out at the night sky and wondered if they were alone in the universe. With the discovery of other planets in our solar system, the true extent of the Milky ...

Oldest-known stone tools pre-date Homo

May 20, 2015

Scientists working in the desert badlands of northwestern Kenya have found stone tools dating back 3.3 million years, long before the advent of modern humans, and by far the oldest such artifacts yet discovered. ...

NASA analyzed the winds of Tropical Storm Ana

May 20, 2015

In mid-May 2015, Ana became the first named tropical storm of the North Atlantic hurricane season. May is early to see large storms in the Atlantic; the season begins in earnest on June 1. But on May 10, ...

Pockmarks on the lake bed

May 18, 2015

An unusual and unexpected discovery: on the floor of Lake Neuchâtel, geologists have happened upon huge underwater craters—some of the largest in the world to be found in lakes. They are not volcanic in ...

When an electron splits in two

May 12, 2015

(Phys.org)—As an elementary particle, the electron cannot be broken down into smaller particles, at least as far as is currently known. However, in a phenomenon called electron fractionalization, in certain ...

Recommended for you

Self-replicating nanostructures made from DNA

7 hours ago

(Phys.org)—Is it possible to engineer self-replicating nanomaterials? It could be if we borrow nature's building blocks. DNA is a self-replicating molecule where its component parts, nucleotides, have specific ...

Could computers reach light speed?

9 hours ago

Light waves trapped on a metal's surface travel nearly as fast as light through the air, and new research at Pacific Northwest National Laboratory shows these waves, called surface plasmons, travel far enough ...

Non-aqueous solvent supports DNA nanotechnology

May 27, 2015

Scientists around the world are using the programmability of DNA to assemble complex nanometer-scale structures. Until now, however, production of these artificial structures has been limited to water-based ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.