The Potentials of Helium Ion Microscopy for Semiconductor Process Metrology
Michael T. Postek, Andras Vladar
Semiconductor manufacturing is always looking for more effective ways to monitor and control the manufacturing process. Helium Ion Microscopy (HIM) presents a new approach to process monitoring which has several potential advantages over the traditional scanning electron microscope (SEM) currently in use in semiconductor 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 ion beam into a smaller probe size relative to that of an electron beam of an SEM. Hence, resolution 2-4 times that of comparable SEMs is theoretically possible. In an SEM, an electron beam interacts with the sample and an array of signals are generated, collected and imaged. This interaction zone may be quite large depending upon the accelerating voltage and materials involved. Conversely, the helium ion beam interacts with the sample, but it does not have as large an excitation volume and thus, the image collected is more surface sensitive and can potentially provide sharp images on a wide range of materials. Compared to an SEM, the secondary electron yield is quite high - allowing for imaging at extremely low beam currents and the relatively low mass of the helium ion, in contrast to other ion sources such as gallium potentially results in minimal damage to the sample. This presentation will report on some of the preliminary work being done on the HIM as a research and measurement tool for semiconductor process metrology being done at NIST.
Proceedings of SPIE
February 24-28, 2008
San Jose, CA
Proceedings of SPIE--the International Society for Optical Engineering
Helium ion, HIM, microscopy, scanning electron microscope, SEM, nanomanufacturing, nanometrology