A research team led by CNSE Professor of Nanoscience Dr. Eric Lifshin is using a new tool in its quest to diminish the persistent problem of contamination in scanning electron microscopes (SEMs). The Evactron 25®, a de-contamination system that provides a safe method for cleaning the inside of SEMs through the use of a stream of reactive gas prior to the examination of specimens, is now on-site at CNSE's Albany NanoTech Complex.
"If samples to be examined are covered with a film of contamination even 10 nanometers thick, that is equivalent to ten billions of a meter," said Lifshin. "The information being observed may be obscured, even with the most advanced electron microscopes, similar to the surface of a street covered with a thin layer of snow."
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| CNSE Professor of Nanoscience Dr. Eric Lifshin is using the Evactron 25 ® to diminish the persistent problem of contamination in SEMs. |
Contamination may be thought of as a two-step process. First, the inside of the microscope absorbs hydrocarbons or other organic molecules. Then, these molecules migrate either as a vapor or through surface diffusion into the path of the SEM's electron beam, where they are chemically modified to create contamination deposits on the surface of the sample being observed. The contamination often appears as a dark layer in SEM images that makes it difficult to see the underlying structure of an integrated circuit chip or other types of samples with fine features.
Now, contamination can be reduced using the Evactron 25 ®, which is attached to the microscope. Prior to the examination of a sample, it creates what is believed to be a stream of chemically active atomic oxygen that sweeps through the inside of the microscope, converting the hydrocarbons to forms that are easily removed from the system by hydrocarbon free
pumps - eliminating the contamination at the source and allowing a clear view of the sample.
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| The Evactron 25®, a de-contamination system that provides a safe method for cleaning the inside of SEMs. |
"We will be regularly using the Evactron to improve the performance of our existing microscopes," said Lifshin. "My team and others will conduct a series of experiments that will enable us to find the optimum conditions to combat contamination of SEMs and other types of equipment that are used for both observing and creating nanoscale structures, including the extreme ultraviolet (EUV) mirrors used in advanced lithography. We will also characterize the contamination and develop a clearer picture of the mechanism by which it is formed."
Lifshin and his team received the new system from XEI Scientific, which donated the Evactron ® to CNSE to help better understand the nature of contamination of electron microscopes. The company makes and sells anti-contamination systems for the electron microscope community.
"Carbon contamination in SEMs limits the imaging capability and interferes with other measurements made in the SEM. The donation of an Evactron ® De-Contaminator to Dr. Lifshin will help his research group push the limits of nanoscale measurements in the SEM by removing carbon contamination from the instrument and specimens," said Ronald Vane, president of XEI Scientific. "We hope that Professor Lifshin is able to achieve exciting new results by combining Evactron ® cleaning with the techniques he is pioneering."
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