An integral field emission “microSEM” for UHV surface analysis

Abstract

It has been recognized for some time that the application of high sensitivity surface analytical techniques at high spacial resolution is highly desirable. For surface characterization, concentration distribution and topography are superior to average concentration, and sensitivity is increased by localizing the analysis to regions of higher concentration. In the field of Auger electron spectroscopy, this trend is reflected by the increasing popularity of scanning AES (SAM) instrumentation.Due to the low yield of characteristic secondary particles (e.g. Auger electrons or X-rays), the central technological challenge is the delivery of relatively large beam currents into sufficiently small probes (often <30nm). However, electron optical design must also provide for optimum detector collection efficiency, for in many cases beam induced alterations and specimen damage rather than electron optics may limit the useable beam current in small probes.Two basic instrumental configurations are in use; the off-axis approach that treats beam generation and signal detection systems as isolated entities, and the coaxial approach in which the electron gun is an integral part of the detector (e.g. cylindrical mirror analyzer).