Dr. Bradley Thiel, associate professor and associate director of metrology at the College of Nanoscale Science and Engineering, is part of a team that recently received a patent for a new type of electron microscope detector.
Thiel began the project while at Cambridge University prior to joining the CNSE faculty in March 2004. The Helix detector combines the high resolution imaging capability of magnetic immersion lens electron optics with the charge control capabilities of low vacuum scanning electron microscopes (SEMs).
With this combination, the team solved a critical problem in scanning electron microscopy. The SEM has been an essential tool for high magnification imaging and analysis of surfaces since the first commercial device in 1965. The development of the Environmental SEM (ESEM) in 1989 extended SEM capability to a much wider range of samples and dynamic experimentation. Thiel has been leading the academic research into the fundamental physics of ESEM since the mid-1990s.
However, until the development of the Helix detector, ESEM could not be applied at the very highest SEM magnifications that are essential for nanotechnology.
The Nova NanoSEM, manufactured by the FEI Company, incorporates a new electron detector that removes this limitation. Thiel was a key member of the team that developed the Helix detector and is listed as one of the inventors on U.S. patent number 6,972,412.
Thiel's research included the development of a dedicated Monte-Carlo program to simulate the path of electrons through mixed electrostatic and magnetic fields in combination with gas collisions. Part of the detector creates the conditions for the classic magnetron motion of electrons in crossed electrostatic and magnetic fields.
Research and development for the Helix detector took more than five years from initial experiments to commercial product. Thiel notes that the detector "is an important enabling technology that we hope will form the basis for next-generation critical-dimension metrology for lithographic masks and microelectronic devices."
"The research on ESEM and the development of the Helix detector is a perfect example of the value of collaborations between commercial companies and academic researchers, and we are pleased to continue the collaboration with Professor Thiel here at Albany," said W. Ralph Knowles, ESEM Technology Manager, FEI Company. "It is very appropriate that the College of Nanoscale Science and Engineering has a Nova NanoSEM as a tool for the study of nanotechnology and to enable further research into the fundamental physics of the ESEM and the Helix detector."
The details of the design, operation and performance of the Helix detector have been published in Applied Physics Letters, Volume 88, page 023105 (January 2006), and Review of Scientific Instruments, Volume 77, page 033705 (2006).
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