Silicon wafers for scanning helium microscopy - art. no. 693740

The Scanning Helium Microscopy is a new technique currently under development. The paper is an overview of measurements of the geometrical characteristics of Silicon wafer concentrating on accuracy and closely related matters. In the microscope the helium atom beam is used as a probe. The overall microscope resolution depends on a deflecting element, which shapes the beam and focuses it onto a sample's surface. The most promising focusing component appears to be an ultra thin silicon wafer that is deformed under a precise electric field. Flatness and thickness uniformity of the wafer must be measured in order to select the best plate to be used in the microscope. A scanning measurement system consists of two coaxially positioned confocal heads. The paper discusses measures taken to overcome the system sensitivity to temperature variation and concludes with utilizing symmetry descriptors for final selection of wafers.