The technique, called Through-Focus Scanning Optical Microscopy (TSOM), has now been shown able to detect tiny differences in the three-dimensional shapes of circuit components, which until very recently have been essentially two-dimensional objects.
The three-dimensional tri-gate (FinFET) transistors shown here are among the 3-D microchip structures that could be measured using NIST's technique for improving through-focus scanning optical microscopy (TSOM).
Credit: Courtesy of Intel Corp.
TSOM is sensitive to features that are as small as 10 nanometers (nm) across, perhaps smaller—addressing some important industry measurement challenges for the near future for manufacturing process control and helping maintain the viability of optical microscopy in electronics manufacturing.
For decades, computer chips have resembled city maps in which components are essentially flat. But as designers strive to pack more components onto chips, they have reached the same conclusion as city planners: The only direction left to build is upwards. New generations of chips feature 3-D structures that stack components atop one another, but ensuring these components are all made to the right shapes and sizes requires a whole new dimension—literally—of measurement capability.
"Previously, all we needed to do was show we could accurately measure the width of a line a certain number of nanometers across," explains NIST's Ravikiran Attota. "Now, we will need to measure all sides of a three-dimensional structure that has more nooks and crannies than many modern buildings. And the nature of light makes that difficult."
Part of the trouble is that components now are growing so small that a light beam can't quite get at them. Optical microscopes are normally limited to features larger than about half the wavelength of the light used—about 250 nanometers for green light. So microscopists have worked around the issue by lining up a bunch of identical components at regular distances apart and observing how light scatters off the group and fitting the data with optical models to determine the dimensions. But these optical measurements, as currently used in manufacturing, have great difficulty measuring newer 3-D structures.
Other non-optical methods of imaging such as scanning probe microscopy are expensive and slow, so the NIST team decided to test the abilities of TSOM, a technique that Attota played a major role in developing. The method uses a conventional optical microscope, but rather than taking a single image, it collects 2-D images at different focal positions forming a 3-D data space. A computer then extracts brightness profiles from these multiple out-of-focus images and uses the differences between them to construct the TSOM image. The TSOM images it provides are somewhat abstract, but the differences between them are still clear enough to infer minute shape differences in the measured structures—bypassing the use of optical models, which introduce complexities that industry must face.
"Our simulation studies show that TSOM might measure features as small as 10 nm or smaller, which would be enough for the semiconductor industry for another decade," Attota says. "And we can look at anything with TSOM, not just circuits. It could become useful to any field where 3-D shape analysis of tiny objects is needed."
*R. Attota, B. Bunday and V. Vartanian. Critical dimension metrology by through-focus scanning optical microscopy beyond the 22 nm node. Applied Physics Letters, DOI: 10.1063/1.4809512, published online June 6, 2013.
Chad Boutin | EurekAlert!
SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University
Molecule flash mob
19.01.2017 | Technische Universität Wien
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences