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Scientists at SUNY College of Nanoscale Science and Engineering develop groundbreaking materials characterization techniques

CNSE graduate student Lakshmanan Vanamurthy and professors Mengbing Huang and Hassaram Bakhru, in collaboration with researchers at IBM, outline novel characterization method to analyze transistor components at the sub-nanometer level

Scientists at SUNY's CNSE
develop ground-breaking
materials characterization techniques
(video)
Pioneering nanoelectronics research led by a team of scientists at the SUNY College of Nanoscale Science and Engineering (CNSE) has been published in the Journal of Vacuum Science and Technology A, which recognized their work for its potential to improve the processes used to create Ultra Shallow Junctions (USJs). These are transistor components that can enhance the efficiency and speed of computer chips, but which can also suffer from imperfections resulting from researchers’ previous inability to accurately quantify, locate, and assess the electrical activation of the “doped” atoms used to fabricate USJs.

CNSE graduate student Lakshmanan Vanamurthy, Associate Professor of Nanoscience Dr. Mengbing Huang, and Nanoscience Constellation Head and Distinguished Service Professor of Nanoscience Dr. Hassaram Bakhru, in conjunction with IBM researchers Dr. Toshiharu Furukawa, Nathaniel Berliner, Joshua Herman, Zhengmao Zhu, Dr. Paul Ronsheim, and Dr. Bruce Doris discovered that by combining ion beam analysis with a nanoscale layer sectioning technique that uses room-temperature oxidation and wet-etching methods, they gained an unprecedented view of USJ impurities at the sub-nanometer level.

By using these techniques in a novel way, the team was able to quantify the number of impurity atoms, in this case boron atoms, that are typically added as part of a process called “doping” to impart certain electrical characteristics to the USJs located a few nanometers within the transistor’s silicon surface. More specifically, the researchers used ion beam analysis, including Rutherford Backscattering Spectrometry, ion channeling, and Nuclear Reaction Analysis to be able to measure the high-energy ions scattered off the sample, or secondary particles that are emitted as the incident ions impinge on the sample. Armed with that knowledge, they then worked backward in order to figure out the number of impurity atoms within the material. Since these ion beam techniques rely on the detection of nuclear events involving high-energy ions and target atomic nuclei, this process also allowed the team to obtain the data without it being compromised by an insufficient knowledge of the chemical and electronic characteristics of the material, which had previously been a research obstacle that diminished the value of the test results.

However, this pioneering work goes one step further. Now, the researchers can not only find out how many impurity atoms have been added and electrically activated in a given USJ, but they can also employ a nanoscale layer sectioning technique to pinpoint where the boron atoms or any defects in the crystal structure of the USJ material are located. This process allows the team to evaluate the added impurities and any material defects at an unprecedented .5 nanometer (or 5 Ångsträm) resolution, even smaller than the size of a silicon unit cell, offering an unmatched capability to characterize USJs and nanomaterials alike.

These original findings were documented in “Subnanometer-resolution depth profiling of boron atoms and lattice defects in silicon ultrashallow junctions by ion beam techniques,” which was featured in the March issue of the Journal of Vacuum Science and Technology A and published by the American Vacuum Society, an interdisciplinary professional organization that boasts approximately 4,500 members worldwide who are involved in a variety of disciplines, including chemistry, physics, biology, mathematics, engineering, and business in order to advance the basic science, technology development, and commercialization of materials, interfaces, and processes. The research article was published for its high impact to the field of nanoelectronics research.

“Working in collaboration with our research partners at IBM, these published findings are the culmination of CNSE’s exceptional efforts to advance nanotechnology-based research and development, and in particular, materials characterization techniques, to further the nanoelectronics industry and enhance the capabilities of computer chips that we all regularly rely on,” said CNSE graduate student Lakshmanan Vanamurthy. “I am thrilled to be a part of this high-tech idea-propagating ecosystem, where a graduate student like myself can work with experts like Professors Huang and Bakhru to break through previous research barriers. This is the place for leading-edge scientific discovery — it couldn’t have happened anywhere else.”

By mapping out the location of the impurity or boron atoms and knowing exactly how many have been implanted and electrically activated in a USJ, or by being able to see the semiconductor’s crystal structure and its defects, researchers will be able to develop new ways to limit deficiencies that are inherent in the chip fabrication process. For instance, by seeing the detailed results of the annealing process, in which heat is applied to restore the lattice structure of the silicon semiconductor material, researchers will likely be able to find more targeted ways of manipulating the atoms, potentially leading to the ability to create more efficient and reliable USJs on an even smaller scale.

“This exciting research greatly expands our ability as researchers to see details that had been elusive until now, providing us with a view so exact that the team is able to observe the segregation of boron atoms, that is, we could decipher the individual atoms and the space between them,” said Nanoscience Constellation Head and Distinguished Service Professor of Nanoscience Dr. Hassaram Bakhru. “The fact that device size has nearly approached previous resolution limits means this research is literally breaking down barriers, something that is only possible through the combined power of CNSE’s resources and its pioneering culture.”

“Being able to characterize materials to such a fine point by using this new methodology will help us to create the best conditions for producing today’s most advanced computer chips,” said CNSE Associate Professor of Nanoscience Dr. Mengbing Huang. “This newfound capability is yet another clear example of an idea that will travel from the lab to the fab, and it is also a testament to how CNSE’s faculty, students, corporate partners, and unparalleled resources combine to enable first-class scientific achievements.”

To view the published article, please visit: http://avspublications.org/jvsta/resource/1/jvtad6/v31/i3/p031403_s1