Transmission Helium Ion Microscopy

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Electronic systems continue to evolve towards smaller sizes, with increased capabilities, while reducing cost and power requirements. One-dimensional device geometries, atomically-thin, two-dimensional, materials, and unusual semiconductors have entered the field. Single electron or photon detectors, emitters, and switches are increasingly reported. A new information bit has developed called a qubit resulting from the quantum size of these new devices. These intriguing new capabilities are not only scientifically fascinating, but are enabling new industries by their application in novel electronic designs. Every development in electronics has occurred in parallel with, or because of, new types of fabrication, imaging and characterization capabilities. Electron microscopy have steadily improved our capabilities for "seeing" complex structures at the atomic scale. Atomic profiling via high-energy helium ion beams, one of the oldest characterization techniques (Rutherford backscattering), was a pivotal tool during the early development of silicon chips for computers and continues to evolve for larger area processing. Liquid metal sources for focussed ion beams of almost any element have revolutionized the fine milling and patterning industry. A single atom tip source for helium ions, combined with a stable focussing column, is providing new opportunities for novel characterization. The aim of this research program is to establish Transmission Helium Ion Microscopy (THIM), for the characterization of the atomic composition and thickness of very thin materials. The HIM ion source emits ions from a tiny volume (one tungsten atom). Accelerated helium atoms easily pass in between the atoms in a solid but begin to slow down rapidly from electrostatic forces. The ability to steer a He ion via rows of atoms (channeling) will be applied to quantify layer thickness and atomic composition from scattering intensities. The presence of contaminants and impurities may be detected by their effects on the energy and phase of the beam. Their detection after passing through a thin sample can tell us much about the sample.  To carry out THIM better cameras will be needed. We will be working with Canadian industry towards future products and manufacturing opportunities. The application of THIM to materials characterization will benefit the Canadian and global electronics industry in general through their need for smaller and more efficient active device properties. The research will likely enable higher resolution detection of electrical properties critical to lasers, light emitting diodes and solar cell applications. The training of personnel in the new advanced techniques proposed here will help Canadian society stay with or ahead of the global community in understanding and designing the next generation of critical electronic materials and devices. Our ability to devise new solutions and create new devices will improve our quality of life.