Research News
Secondary electron images obtained by the HIM on a gold-on-carbon sample (Field-of-view = 1.5 μm).
NIST Advancing Nanoscale Research with New Helium Ion Microscope
Helium Ion Microscopy (HIM) is a new particle beam imaging and measurement methodology. The first commercial HIM has been installed at NIST within the Manufacturing Engineering Laboratories. (MEL), Precision Engineering Division (PED). A research program within PED is studying the imaging mechanisms, modeling, analytical capabilities and uncertainties regarding dimensional measurements made with this microscope. This fundamental research is of extreme interest for application to accurate metrology for US semiconductor manufacturing. In addition, an initial PED collaboration with the Surface and Microanalysis Science Division of the Chemical Science and Technology Laboratory (CSTL) will explore a number of chemical spectroscopies including helium ion induced analogs of: UPS (ultraviolet photoelectron spectroscopy) and IPES (inverse photoelectron spectroscopy) INS (ion neutralization spectroscopy), and LEIS (low-energy ion scattering spectroscopy). The Nanomechanical Properties and Processing Characterization Groups within Materials Science and Engineering Laboratory (MSEL) are also collaborating to take advantage of the expected high surface sensitivity and the low surface sputtering damage characteristics of the microscope to generate more accurate images of surface topography, surface features, or nanoscale entities that can be used to calibrate or verify measurements obtained using contact or near-contact scanned probe techniques.
Secondary electron images obtained by the HIM on a gold-on-carbon sample (Field-of-view = 1.5
μm).
The HIM is unique but, in many ways, complementary to the traditional scanning electron microscope (SEM). HIM potentially poses several imaging advantages over SEMs currently in use in research and manufacturing facilities across the world. Due to the very high source brightness, and the shorter wavelength of the helium ions, it is theoretically possible to focus the helium ion beam into a smaller probe size relative to that of an electron beam of an SEM, hence higher resolution is possible. In an SEM, an electron beam interacts with the sample and a variety of signals are generated, collected and imaged. This interaction zone may be quite large depending upon the electron energy and sample material. Conversely, when the helium ion beam interacts with the sample, it does not have as large an excitation volume and thus the image collected is more surface sensitive and contains more surface detail.
NIST is also using the HIM in its current cross-laboratory Innovations in Measurement Science (IMS) Program titled ”Metrology for the ‘Fate&rsquo of Nanoparticles in Biosystems,” which calls for the development of sample preparation methodology for imaging and dimensional measurements of nanoparticles in biological systems for investigations at the nanoscale. The unique HIM technology will facilitate this program in its mission and in the support of NIST nanomanufacturing research.
Orion Helium Ion Microscopy (HIM)